Active Depth Sensing Image Sensor

Abstract

Aspects of the present disclosure relate to an image sensor. An example device includes an image sensor comprising one or more pixels. Each of the one or more pixels includes a photodetector, and the photodetector includes a photosensitive surface comprising germanium. In some embodiments, the photodetector includes a photodiode, which includes an intrinsic silicon layer doped with germanium or including a germanium crystal. The intrinsic layer can be located between a p-layer and an n-layer that do not contain germanium. The intrinsic layer can be configured to absorb photons of light received at the intrinsic layer. The light may include one or more reflections of emitted light for active depth sensing. For example, the emitted light may be frequency modulated and have a first wavelength for indirect time-of-flight depth sensing. The sampling circuit may generate a voltage indicating a phase difference between the emitted light and the reflection of the emitted light.

Description

[0001] Priority declaration

[0002] This patent application claims the benefit of U.S. Non-Provisional Application No. 16 / 735,084, filed on January 6, 2020, entitled “ACTIVE DEPTH SENSING IMAGE SENSOR,” which application has been assigned to its assignee and is hereby expressly incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to systems and methods for active depth sensing, and more particularly to active depth sensing image sensors. Background Art

[0004] Devices can use different active depth sensing systems to determine the distance of their surroundings. When determining the depth, the device can generate a depth map by transmitting one or more wireless signals and measuring the reflection of the wireless signals from the scene, which shows or otherwise indicates the depth of the object relative to the device. One type of active depth sensing system is a time-of-flgiht (TOF) system. For optical TOF systems (such as Light Detection and Ranging (LIDAR) sensors), pulses of light are emitted and reflections of the pulses of light are received. The round-trip time of light from the transmitter to the receiver is determined based on the pulses, and the distance or depth between the object reflecting the emitted light and the TOF system is determined based on the round-trip time. Summary of the invention

[0005] This Summary is provided to introduce selected concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0006] Aspects of the present disclosure relate to an image sensor. An example device includes an image sensor including one or more pixels. Each of the one or more pixels includes a photodetector, and the photodetector includes a photosensitive surface including germanium. In some embodiments, the photodetector includes a photodiode, which includes an intrinsic silicon layer doped with germanium or including crystalline germanium (which may be referred to as a germanium crystal). The intrinsic layer may be located between a p-layer and an n-layer that do not contain germanium. The intrinsic layer may be configured to absorb photons of light received at the intrinsic layer. The light may include one or more reflections of emitted light for active depth sensing. For example, the emitted light may be frequency modulated and have a first wavelength for indirect time-of-flight depth sensing. The sampling circuit may generate a voltage indicating a phase difference between the emitted light and the reflection of the emitted light.

[0007] In another example, a method includes receiving light at a photosensitive surface of a photodetector of a pixel of an image sensor. The photosensitive surface includes germanium. The method also includes absorbing photons of light by the photosensitive surface and generating a current based on the absorbed photons.

[0008] In another example, a non-transitory computer-readable medium storing instructions is disclosed. Execution of the instructions by one or more processors of a device causes the device to receive light at a photosensitive surface of a photodetector of a pixel of an image sensor of the device. The photosensitive surface includes germanium. Execution of the instructions also causes the device to absorb photons of light through the photosensitive surface and generate a current through the photodetector based on the absorbed photons.

[0009] In another example, an example apparatus is disclosed that includes components for receiving light at a photosensitive surface of a photodetector of a pixel of an image sensor. The photosensitive surface includes germanium. The apparatus also includes components for absorbing photons of light by the photosensitive surface and components for generating a current based on the absorbed photons. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Various aspects of the present disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.

[0011] Figure 1 is a depiction of a direct TOF system.

[0012] Figure 2 is a depiction of an indirect TOF system.

[0013] Figure 3 is a depiction of an image sensor for an indirect TOF system.

[0014] Figure 4 is a depiction of the demodulated pixels.

[0015] Figure 5 It is a depiction of a 2-phase demodulated pixel.

[0016] Figure 6 It is a depiction of 3-phase demodulated pixels.

[0017] Figure 7 It is a depiction of 4-phase demodulated pixels.

[0018] Figure 8 is a depiction of a portion of a circuit including a photodiode configured to be coupled to one or more sampling circuits.

[0019] Fig. 9 is a depiction of a portion of a circuit including a horizontal pin photodiode configured to be coupled to one or more sampling circuits.

[0020] Fig. 10A is a depiction of a vertical pin photodiode.

[0021] Fig. 10B is a depiction of a horizontal pin photodiode.

[0022] Fig.11 is a block diagram of an example device including a TOF system.

[0023] Fig.12 is a flow chart depicting an example operation of an image sensor. DETAILED DESCRIPTION

[0024] Aspects of the present disclosure may be used in active depth sensing systems, such as TOF systems. TOF systems are used to determine depth and are found in many applications today, including radio detection and ranging (RADAR), sound navigation and ranging (SONAR), and light detection and ranging (LIDAR). For example, many autonomous vehicles (such as unmanned aerial vehicles (UAVs) and autonomous cars) include one or more LIDAR systems, and the LIDAR systems are used to detect obstacles in order to guide the vehicle.

[0025] Optical TOF systems can emit and receive reflections of light. Many optical TOF systems (such as some LIDAR systems) may use near-infrared (NIR) light. In some embodiments, NIR light can be defined as having a wavelength from 700 nanometers to 1000 nanometers. For example, a LIDAR system can use light with a wavelength of 830 nanometers or 940 nanometers. The optical TOF system includes one or more photodetectors designed to receive reflections of emitted light from the transmitter of the TOF system. However, when the TOF system uses light with a wavelength of 830 nanometers or 940 nanometers, ambient light and interference may block the reflection of the emitted light. For example, most of the energy emitted by the sun has a wavelength below 1000 nanometers (such as visible light and infrared light with a wavelength below 1000 nanometers). Therefore, the reflection received by the photodetector may be blocked in bright sunlight, and the TOF system may have difficulty in accurately determining the depth.

[0026] In order to reduce the interference caused by background radiation (such as sunlight), the optical TOF system can use a signal with a wavelength greater than 1000 nanometers (or greater than 1400 nanometers). For example, the optical TOF system can emit light with a wavelength of about 1100 nanometers (or other wavelengths with less interference caused by ambient light than 830 nanometers or 940 nanometers). The photosensitive surface of the photodetector configured to absorb photons to provide current can be silicon. As the wavelength increases to more than 1000 nanometers, silicon gradually loses the efficiency of photon absorption. For example, compared with absorbing light of 1000 to 1400 (or greater) nanometers, a silicon-based photosensitive surface photodiode absorbs light with a wavelength of 800 to 1000 nanometers more efficiently. In fact, the silicon-based photosensitive surface may not be able to absorb light with a wavelength greater than 1100 nanometers.

[0027] In some embodiments, the image sensor may include one or more photodiodes having a photosensitive surface having a compound different from pure silicon. The compound may be configured to absorb light having a wavelength at least greater than 1000 nanometers. For example, the photodiode may have a photosensitive surface comprising a silicon-germanium compound to increase the photodiode's absorption efficiency for light having a wavelength greater than 1000 nanometers. In another example, the photodiode may have a photosensitive surface comprising a silicon-free germanium crystal to increase the photodiode's absorption efficiency for light having a wavelength greater than 1400 nanometers. In this way, the optical TOF system can use light having a wavelength greater than 1000 nanometers (or 1400 nanometers) for depth sensing.

[0028] One advantage of using higher wavelength light is that the TOF system is less affected by ambient light and interference, which increases the signal-to-noise ratio of the light sensed at the photodiode and the effective range of the TOF system. Another advantage of using light with a wavelength greater than 1400 nanometers is that this light is considered safer for the eyes than light with a wavelength below 1400 nanometers (which may be received at the retina and cause damage to the eyes). For example, light that can be considered to cause retinal damage can have a wavelength in the range of 400 nanometers (ultraviolet light) to 1400 nanometers (which can be SWIR light). For eye safety considerations, the intensity of light in this range may be limited. However, the intensity of emitted light with a wavelength greater than 1400 nanometers can be safely increased relative to the intensity of light with a wavelength of 830 nanometers, for example, of the TOF system, because light with a higher wavelength will not be absorbed by the retina and cause damage. Increasing the light intensity will increase the signal-to-noise ratio of the light sensed at the photodiode, which can increase the effective range and data quality of the TOF system. Various aspects of photodetectors and image sensors for TOF systems are described herein. Although examples of infrared light are provided (such as light with a wavelength greater than 1000 nanometers, light with a wavelength greater than 1400 nanometers, light with a wavelength of 830 nanometers, and light with a wavelength of 940 nanometers), any suitable spectrum signal can be used for a TOF system. The light can be within the visible spectrum (such as visible to the naked eye), or the light can be outside the visible spectrum (such as ultraviolet and infrared light). In addition, any suitable infrared light can be used, including NIR, short-wave infrared (SWIR), and far infrared (FIR). In some embodiments, SWIR can refer to a wavelength between 1000 nanometers and 2500 nanometers. Infrared can also refer to light within and outside the visible spectrum. Therefore, the present disclosure is not limited to the examples of the wavelengths of the emitted light provided.

[0029] A TOF system can be a direct TOF system or an indirect TOF system. A direct TOF system transmits a pulse, senses the pulse, and determines the time difference between the transmitted pulse and the reflection of the sensed pulse. A direct TOF system uses this time difference to determine the round trip time, thereby determining the depth of the object relative to the TOF system.

[0030] Figure 1 1 is a depiction of an example direct TOF system 100. Direct TOF system 100 includes a transmitter 102 and a receiver 108. Transmitter 102 may also be referred to as a "projector" or "emitter" and is not limited to a specific transmitting component. Receiver 108 may be referred to as a "detector," "sensor," "sensing element," or "photodetector" and is not limited to a specific receiving component.

[0031] Emitter 102 may be configured to emit a signal, such as light 104, toward a scene including surface 106. Although emitted light 104 is shown as being directed toward surface 106, the field of emission of emitter 102 may extend beyond the dimensions of surface 106. For example, a TOF system emitter may have a fixed focal length lens that defines the field of emission of the emitter.

[0032] The emitted light 104 includes light pulses 114 at known time intervals (e.g., defined time periods). The receiver 108 includes an image sensor 110 to sense reflections 112 of the emitted light 104. The reflections 112 include reflected light pulses 116, and the TOF system determines a round trip time 122 of the light by comparing the timing 118 of the emitted light pulses 114 with the timing 120 of the reflected light pulses 116. The distance of the surface 106 from the TOF system can be calculated as half the round trip time multiplied by the emission speed (e.g., the speed of light for light emission). The depth can be determined using the following equation (1):

[0033]

[0034] Where D is the depth of the surface 106 relative to the direct TOF system 100 and c is the speed of light (based on the emitter 102 emitting the light 104).

[0035] The image sensor 110 may include an array of photodiodes and components to sense reflections and generate an array of currents or voltages corresponding to the intensity of the received light. Each entry in the array may be referred to as a pixel or cell. Over time, the TOF system may compare the voltage (or current) from the pixel to detect reflections 112 of the emitted light 104. For example, the TOF system may compare the signal to a threshold (corresponding to noise, such as ambient light), and the TOF system may identify peaks greater than the threshold as reflected light pulses 116 sensed by the image sensor 110. The threshold may be based on ambient light or other interference. For example, there may be a certain amount of ambient light (no emitted light 104), and the threshold may be based on the size of the ambient light (such as measured by the image sensor 110). The upper limit of the effective range of the TOF system may be such a distance that the noise or attenuation of the signal before sensing the reflection causes the signal-to-noise ratio (SNR) to become too large so that the sensor cannot accurately sense the reflected light pulse 116. To reduce interference (and thereby increase range or improve signal-to-noise ratio), receiver 108 may include a bandpass filter prior to image sensor 110 to filter incident light outside the wavelength range of emitted light 104 .

[0036] Direct TOF systems may be susceptible to interference (such as ambient light or other noise) that may obscure pulses in the reflection received at the image sensor 110. Therefore, each pixel of the image sensor 110 of the direct TOF system may include a single-photon avalanche diode (SPAD) due to the sensitivity and responsiveness of the single-photon avalanche diode (SPAD) to be able to identify pulses in the reflection and distinguish the arrival time of the pulsed light reflection. However, SPAD-based depth sensing makes a trade-off between spatial resolution and background light suppression capabilities. Increasing spatial resolution reduces the ability to distinguish pulses from ambient light. In addition, the area required for the SPAD's readout circuit, time-dependent time-to-digital converter (TDC), and storage unit of the image sensor 110 reduces the available space for other components of the direct TOF system or other systems.

[0037] Another TOF system is an indirect TOF system (which may also be referred to as a Frequency Modulated Continuous Wave (FMCW) TOF system). An indirect TOF system transmits a periodic signal (such as a continuous wave sinusoidal signal or a periodic pulse of light), senses the reflection of the signal, and determines the phase difference between the transmitted signal and the sensed signal reflection. The indirect TOF system uses this phase difference to determine the depth of the object relative to the TOF system.

[0038] Figure 2 is a depiction of an example indirect TOF system 200. Indirect TOF system 200 includes a transmitter 202 and a receiver 208. Transmitter 202 may be configured to transmit a signal (such as light 204) toward a scene including a surface 206. Although transmitted light 204 is shown as being directed toward surface 206, the field of emission of transmitter 202 may extend beyond the dimensions of surface 206. For example, a TOF system transmitter may have a fixed focal length lens that defines the field of emission of the transmitter.

[0039] The emitted light 204 includes a sinusoidal signal 214 (or other suitable periodic signal) of a defined frequency. The receiver 208 includes an image sensor 210 for sensing a reflection 212 of the emitted light 204. The reflection 212 includes a reflected sinusoidal signal 216. The indirect TOF system 200 determines a phase difference 222 between the emitted sinusoidal signal 214 and the reflected sinusoidal signal 216 (as shown in the emitted sinusoidal timing 218 and the reflected sinusoidal timing 220). The phase difference 222 can indicate a round trip time and can thus be used to determine the distance of the surface 206 from the indirect TOF system. In order to generate the sinusoidal signal 214, the TOF system 200 can be configured to modulate a carrier signal to generate a sine wave. For example, light of 940 nanometer wavelength can be modulated to form the sinusoidal signal 214. The frequency of the wave can be referred to as the modulation frequency in this article. When comparing the relationship between TOF and phase difference, the measured phase difference (PD) and the modulation frequency (f mod ) is used to define TOF, as shown in the following equation (2):

[0040]

[0041] In a simplified example, if PD is π and f mod = is approximately 250 kilohertz (kHz), then the TOF is 2 microseconds (1 divided by 500 kHz). Referring back to equation (1), the depth D based on a TOF equal to 2 microseconds is approximately 300 meters.

[0042] although Figure 2 The emission signal is shown as having a sinusoidal waveform, but any suitable waveform may be used. For example, the TOF system may be configured to gradually increase and decrease the intensity of the emitted light in a periodic pattern. In this way, the waveform of the emitted light may approximate a square wave (such as for a periodic pulse signal). Other waveforms may be used, including sawtooth waveforms, etc. As used herein, a sinusoidal waveform or wave may refer to any suitable waveform of a signal (including an approximate square wave).

[0043] In some embodiments, the indirect TOF system 200 may include a demodulation circuit for each pixel (referred to herein as a demodulation pixel or a lock pixel) of the image sensor 210. Each demodulation pixel may include a demodulation photodetector and may be configured to generate and store one or more voltages corresponding to the phase or phase difference of the reflected sinusoidal signal and the transmitted sinusoidal signal received at the photodiode of the array. The phase difference may be determined based on one or more stored voltages. For example, the demodulation pixel may generate a voltage signal (such as using the current from the photodiode to determine whether to send a pixel voltage (such as a trunk voltage) or a low voltage as the voltage signal). The example image sensor 210 using the demodulation pixel may generate a voltage array for a single capture of the image sensor 210. The voltage array may be processed to generate a PD for each pixel. Figure 3 An example indirect TOF image sensor is shown, and Figure 4 Demodulated pixels of an example image sensor are shown.

[0044] Figure 3 is a depiction of an indirect TOF image sensor 300. The image sensor 300 may be Figure 2 2. An example implementation of an image sensor 210 in FIG. The image sensor 300 includes an array 302 of pixels 304, a column amplifier 306, a column comparator 308, a column counter 310, a column multiplexer (MUX) 312, a digital controller 314, a transmit (TX) delay controller 316, a TX driver / row controller 318, a reference signal / ramp generator 320, and a bias circuit 322. The size of the array 302 can be M rows×N columns of pixels 304. In some embodiments, the size of the array 302 can be 512×512 pixels. Each pixel 304 can include a demodulation pixel. The pixels 304 can be arranged so that the array has a pitch of 5 microns×5 microns. In some other embodiments, the pitch can be 7.5 microns×7.5 microns (such as, for a 256×256 pixel array 302).

[0045] The image sensor 300 may be configured to drive the pixel rows of the array to absorb photons and generate voltages corresponding to the absorbed photons. For example, the TX driver / row controller 318 may receive signals from the digital controller 314 and provide signals to one or more of the rows of the array 302 to drive those pixels 304 and obtain readings from the array 302. The driven pixels 304 may provide the stored voltage to the column amplifier 306, which amplifies the signal received from the driven row of the pixel 304. The amplified signal is provided to the column comparator 308, the column counter / latch 310, and the column MUX 312 for processing before being output by the image sensor 300. The digital controller 314 may be configured to control the operation of the comparator 308, the counter 310, and the MUX 312.

[0046] The column comparator 308 can be configured to compare the amplified signal from the pixel 304 with a threshold voltage to determine the value of the voltage from the pixel 304. For example, the reference / ramp generator 320 can provide a ramp voltage to the comparator 308 for each reading from the array 302. If the ramp voltage rises, the comparator can compare the received voltage from the pixel 304 with the ramp voltage until the ramp voltage is greater than the voltage from the pixel 304. In this way, when the two voltage levels cross each other, the comparator 308 can convert the voltage from the pixel 304 to a value corresponding to the ramp voltage. The value can be provided to the counter 310 to add the value over multiple readings, and the added value can be provided to the MUX 312 at a determined time. The MUX 312 can then combine the values ​​of the output from the image sensor 300, and the output can be used by the TOF system (such as a signal processor or controller) to determine the depth of the object relative to the corresponding pixel 304 of the image sensor 300.

[0047] The TOF transmitter may have a delay when transmitting modulated light. To compensate for the delay, the image sensor 300 can be configured to delay driving the rows of the array 304. For example, the digital controller 314 can control the TX delay controller 316 to delay the TX driver / row controller 318 driving one or more rows of the array 302 by an amount of time corresponding to the delay.

[0048] The intensity of the emitted light decreases as it passes through the scene and is reflected by one or more objects. Therefore, the intensity of the reflected light received at the image sensor 300 is less than the intensity of the emitted light at the transmitter of the TOF system. To compensate, the image sensor 300 can combine a bias voltage with the voltage from the pixel 304. For example, the reference / ramp generator 320 can provide a reference signal (such as a bias current) to the bias circuit 322, and the bias circuit 322 can convert the reference signal into a bias voltage applied to the columns of the array 302.

[0049] As described above, each pixel 302 may be a demodulation pixel. The demodulation pixel may sample each wavelength multiple times to prevent uncertainty in determining the phase of the reflected signal (because a value may appear twice within a π wavelength of a sine wave). For example, a 2-phase demodulation pixel may sample each wavelength twice (such as at 0 and π), a 3-phase demodulation pixel may sample each wavelength three times (such as at 0, 2 / 3π, and 4 / 3π), and a 4-phase demodulation pixel may sample each wavelength four times (such as at 0, 1 / 2π, π, and 3 / 2π).

[0050] Figure 4 4 is a depiction of a demodulation pixel 400 of an indirect TOF system. The demodulation pixel 400 is an example of a 2-phase demodulation pixel. The demodulation pixel 400 may be Figure 3 4. The demodulation pixel 400 may be shown in simplified form to explain various aspects of the pixel. For example, although not shown, the demodulation pixel 300 may include one or more readout lines, filtering components, voltage rails, reset switches, and other components.

[0051] The demodulation pixel 400 includes a photodiode 402, a first transistor 404, a second transistor 406, a first capacitor 412, and a second capacitor 414. The photodiode 402 is configured to convert received light (including reflected light from the emitter and ambient light) into a current. If the pixel 400 samples during the first half of the phase of the reflection signal (such as when the reflection sinusoidal signal has a phase of 1 / 2π), the current can be higher than the current sampled during the second half of the phase.

[0052] The first transistor 404 is configured to receive a current from the photodiode 402 and output a voltage V1 to be stored in the capacitor 412 based on the current. In some embodiments, when the current from the photodiode 402 is high and the first transistor 404 is closed, the voltage V1 can be a voltage from a voltage rail (not shown) of the demodulation pixel 400. The operation of the first transistor 404 is controlled by a representation of the emission signal 408. In this way, the transistor 404 can enable the capacitor 412 when the phase of the emission signal 408 is between 0 and π, and the transistor 404 can disable the capacitor 412 when the phase of the emission signal 408 is between π and 2π. As used herein for the demodulation pixel, the emission signal can be a voltage signal having a frequency corresponding to the modulation frequency of the emitted light.

[0053] The second transistor 406 is configured to receive current from the photodiode 402 and output a voltage V2 to be stored in the capacitor 414. In some embodiments, when the current from the photodiode 302 is high and the second transistor 406 is closed, the voltage V2 can be a voltage from a voltage rail (not shown) of the demodulation pixel 400. The operation of the second transistor 406 is controlled by a representation of the inverted emission signal 410 (such as, the emission signal 408 shifted by π). In this way, when the phase of the inverted emission signal 410 is between 0 and π, the transistor 406 can disable the capacitor 414, and when the phase of the inverted emission signal 410 is between π and 2π, the transistor 406 can enable the capacitor 414. The voltages V1 and V2 can be read out and compared to determine the phase difference between the reflected signal and the emission signal. For example, if V1 switches from low to high when the emission signal 408 is high, the phase difference can be between 0 and π. If V2 switches from low to high when the inverted transmit signal 410 is high, the phase difference can be between π and 2π. The demodulation pixel 400 may include additional transistor and capacitor pairs (not shown) to increase the number of phases sampled. For an example 3-phase demodulation pixel, one additional transistor and capacitor pair may be coupled to the photodiode 402 (similar to transistors 404 and 406), and the transistors may be controlled by transmit signals having different phase offsets (such as transmit signal 408, a 2 / 3π phase offset relative to transmit signal 408, and a 4 / 3π phase offset relative to transmit signal 408). For an example 4-phase demodulation pixel, two additional transistor and capacitor pairs may be coupled to the photodiode 402 (similar to transistors 404 and 406), and the transistors may be controlled by transmit signals having different phase offsets (such as transmit signal 408, a 1 / 2π phase offset relative to transmit signal 408, a π phase offset relative to transmit signal 408, and a 3 / 2π phase offset relative to transmit signal 408). Figure 5An implementation of a 2-phase demodulated pixel is shown in FIG. Figure 6 An embodiment of a 3-phase demodulated pixel is shown in FIG. Figure 7 An implementation of a 4-phase demodulated pixel is shown in FIG.

[0054] Figure 5 is a depiction of an embodiment of a 2-phase demodulation pixel 500. The demodulation pixel 500 may be Figure 4 Implementation of the demodulation pixel 400 in FIG. The demodulation pixel 500 includes a photodiode 502, a first phase sampling circuit 504, and a second phase sampling circuit 506. In some implementations, the first phase sampling circuit 504 can have the same configuration as the second phase sampling circuit 506. The difference between the first phase sampling circuit 504 and the second phase sampling circuit 506 can be that tap 1 receives a transmission signal with a first phase offset (such as a 0 phase offset) to enable the circuit 504, and tap 2 receives a transmission signal with a second phase offset (e.g., a π phase offset) to enable the circuit 506. In some implementations, a higher phase demodulation pixel (e.g., a 3-phase demodulation pixel or a 4-phase demodulation pixel) can include additional sampling circuits.

[0055] Figure 6 6 is a depiction of an embodiment of a 3-phase demodulation pixel 600. The 3-phase demodulation pixel 600 includes a photodiode 602, a first sampling circuit 604, a second sampling circuit 606, and a third sampling circuit 608. The 3-phase demodulation pixel 600 may be similar to Figure 5 , except that the 3-phase demodulation pixel 600 includes an additional sampling circuit 608. The third sampling circuit 608 can be enabled based on the tap 3 receiving the transmission signal with the third phase offset. In this way, the sampling by the three sampling circuits 604, 606 and 608 can be performed for different phase offsets of the transmission signal.

[0056] Figure 7 is a depiction of an embodiment of a 4-phase demodulation pixel 700. The 4-phase demodulation pixel 700 includes a photodiode 702, a first sampling circuit 704, a second sampling circuit 706, a third sampling circuit 708, and a fourth sampling circuit 710. The 4-phase demodulation pixel 700 may be similar to Figure 6 , except that the 4-phase demodulation pixel 700 includes an additional sampling circuit 710. The fourth sampling circuit 710 can be enabled based on tap 4 receiving a transmission signal with a fourth phase offset. In this way, sampling by the four sampling circuits 704, 706, 708, and 710 can be performed for different phase offsets of the transmission signal (such as 0, 1 / 2π, π, and 3 / 2π). Although evenly spaced phase offsets are described in some examples, any suitable phase offset (and spacing of such phase offsets) may be employed.

[0057] Figures 5 to 7 Each of the photodiodes 502, 602, and 702 in is coupled to a corresponding sampling circuit of a demodulation pixel, respectively. The photodiode of the demodulation pixel can provide a current corresponding to the photons received at the photosensitive surface of the photodiode to each of the sampling circuits. As described above, when the wavelength of the light received at the photosensitive surface is greater than 1000 nanometers, a photodetector (such as a photodiode) having a pure silicon photosensitive surface may not be able to effectively absorb photons to generate a current. In some embodiments, the photodetector may include a photosensitive surface including non-silicon elements to improve the absorption of light with a wavelength greater than 1000 nanometers. For example, a pin photodiode may include a photosensitive intrinsic layer that is not pure silicon. In some embodiments, the photosensitive surface may include germanium. For example, the intrinsic layer of a pin photodiode may include a combination of silicon and germanium. In some other embodiments, the photosensitive surface may be crystalline germanium. For example, if the wavelength of the emitted light to be received is greater than 1400 nanometers, the intrinsic layer of the photodiode may be crystalline germanium without silicon or other elements.

[0058] Figure 8 is a depiction of a portion of a circuit 800 including a photodiode 802 configured to be coupled to one or more sampling circuits. As shown, the photodiode 802 is a vertical pin photodiode that includes a p-doped region 804, an n-doped region 806, and an intrinsic region 808 between regions 804 and 806. In some embodiments, two contacts from a metal 1 (M1) layer can be coupled to the photodiode 802 to control operation.

[0059] For a pin photodiode 802, an intrinsic layer 808 can be exposed to incident light (at a demodulation pixel), and the intrinsic layer 808 can be configured to absorb received photons so that the photodiode 802 generates a current to an n-well in a p-epitaxial layer 812 on a substrate 810 of a silicon chip. When a transmit (TX) field effect transistor (FET) 814 is enabled, the current from the photodiode 802 can be provided to a contact 818 via the n+ well. When the contact 818 is disconnected, the n+ well can store floating charge from the photodiode 802. The contact 818 can be coupled to one or more sampling circuits (such as Figures 5 to 7 ), and when the sampling circuit is enabled, the current from the photodiode 802 can be provided to the sampling circuit.

[0060] Circuit 800 may also include a contact 820 for resetting the charge from photodiode 802. The reset signal may enable reset (RST) FET 816 to discharge floating charge from the n+ well coupled to contact 818 to another n+ well. As shown, the n+ well may be included in the p-well. In order to isolate the portion of the silicon chip corresponding to the photodiode 802 from other components (such as to prevent parasitic interference or leaching), the p-well may include a shallow trench insulator (STI). As shown, one or more contacts (such as contacts 818 and 820, or contacts coupled to photodiode 802) may be coupled to one or more metal layers (e.g., M1 layer and / or metal 2 (M2) layer) of the circuit.

[0061] As pointed out, Figure 8 A vertical pin photodiode 802 is depicted in which the layers are stacked vertically. In some other implementations, the photodiode may be a horizontal pin photodiode. For a horizontal pin photodiode, the layers are stacked horizontally.

[0062] Fig. 9 9 is a diagram of a portion of a circuit 900 including a horizontal pin photodiode 902 configured to be coupled to one or more sampling circuits. As shown, the circuit and silicon chip configuration for Figure 8 The photodiode 902 in FIG. 8 and the photodiode 802 may be identical. The photodiode 902 includes a horizontally stacked p-doped region 904, an intrinsic region 908, and an n-doped region 906. The intrinsic layer 908 is exposed to light received at the demodulation pixel, and the intrinsic layer 908 is configured to absorb the received photons so that the photodiode 902 provides current to the n-well.

[0063] In order to increase the intrinsic region 808 (in Figure 8 In some embodiments, the intrinsic region may be silicon doped with germanium during fabrication of the photodiode. In another example, the material may be crystalline germanium.

[0064] Fig. 10A is a depiction of a vertical pin photodiode 1000. The vertical pin photodiode 1000 may be Figure 81000 includes a vertically stacked p-layer 1002, an n-layer 1004, and an intrinsic layer 1006. The intrinsic layer 1006 includes silicon doped with germanium or a material containing only germanium (such as the atomic structure Si depicted). 1-x Ge x , where x is greater than 0 and x is less than or equal to 1). In some embodiments, the p-layer 1002 and the n-layer 1004 are not doped with germanium, or do not contain germanium. In this way, the germanium intrinsic layer 1006 can be located between silicon layers that do not contain germanium. Fig. 10B 1 is a depiction of a horizontal pin photodiode 1050. Photodiode 1050 includes a horizontally stacked p-layer 1052, an n-layer 1054, and an intrinsic layer 1056. Horizontal pin photodiode 1050 may be Fig. 9 Implementation of the photodiode 900 in FIG. The intrinsic layer 1056 includes silicon doped with germanium or a material containing only germanium (such as the atomic structure Si depicted). 1-x Ge x , where x is greater than 0 and x is less than or equal to 1). In some embodiments, the p-layer 1052 and the n-layer 1054 are not doped with germanium, or do not contain germanium. In this way, the germanium intrinsic layer 1056 can be located between silicon layers that do not contain germanium. For silicon doped with germanium, the amount of germanium doped into the silicon can be any suitable amount, so that the ratio of silicon atoms to germanium atoms can be any suitable ratio. In some other embodiments, the intrinsic layer can be a material other than silicon (such as germanium or germanium doped with another element). By introducing another element (e.g., germanium), the photodiode can more efficiently absorb photons from light with a wavelength greater than 1000 nanometers (such as, the germanium-doped silicon in the photodiode has a wavelength of 1000 to 1400 nanometers, or the crystalline germanium in the photodiode has a wavelength greater than 1400 nanometers).

[0065] For one or more pixels, the image sensor may include a photodetector having a photosensitive surface including germanium. For example, each demodulation pixel of the image sensor array may include a photodiode, and the photodiode may include an intrinsic layer of silicon doped with germanium (or pure germanium without silicon). Although examples are described with respect to a silicon photosensitive region doped with germanium, these examples are also applicable to other materials, including germanium crystals (as described herein).

[0066] The image sensor may be included in a receiver for active depth sensing. For example, the image sensor may be included in a receiver of a TOF system (such as an indirect TOF system) for determining the depth of the surface of one or more objects relative to the TOF system. The demodulation pixel may be any suitable configuration for determining the phase difference between the light emitted by the emitter of the indirect TOF system and the reflection of the light received by the receiver of the indirect TOF system. For example, the demodulation circuit may be a 2-phase demodulation circuit, a 3-phase demodulation circuit, a 4-phase demodulation circuit, or other suitable phase demodulation circuit. The demodulation circuit may include filtering or processing components (such as for background light elimination or reduction, wave drift compensation, etc.).

[0067] An active depth sensing system (such as an indirect TOF system) including an image sensor can be included in any suitable device. For example, an image sensor including one or more demodulation pixels having a germanium-doped intrinsic layer photodiode can be included in a LIDAR system coupled to a vehicle (e.g., a car or UAV) for autonomous operation of the vehicle. In another example, the image sensor can be included in a wireless communication device (such as a smart phone, tablet computer, etc.). In another example, the image sensor can be included in a handheld device (such as a digital camera, rangefinder, etc.). The image sensor can be included in any suitable device for active depth sensing.

[0068] Fig.11 1 is a block diagram of an example device 1100. The example device 1100 may include an active depth sensing system. In some other examples, the active depth sensing system may be coupled to the device 1100. The example device 1100 may include a transmitter 1101, a receiver 1102, a processor 1104, a memory 1106 storing instructions 1108, and a controller 1110 (which may include one or more signal processors 1112). The device 1100 may optionally include (or be coupled to) a display 1114 and multiple input / output (I / O) components 1116. The device 1100 may include additional features or components not shown. For example, the device 1100 may include a wireless interface, which may include multiple transceivers and a baseband processor for wireless communication. The device 1100 may also include a power supply 1118, which may be coupled to the device 1100 or integrated into the device 1100.

[0069] Transmitter 1101 and receiver 1102 may be part of an active depth sensing system. For example, transmitter 1101 may be transmitter 202, and receiver 1102 may be Figure 2Receiver 204 of indirect TOF system 200. The active depth sensing system can be controlled by controller 1110 (such as signal processor 1112) and / or processor 1104. Transmitter 1101 can include or can be coupled to one or more power supplies that are used to adjust power to cause pulses or modulation of emitted light. Receiver 1102 can be configured to receive reflections of emitted light from transmitter 1101.

[0070] Receiver 1102 may include one or more image sensors including a photodetector having a photosensitive surface including germanium. For example, receiver 1102 may include an image sensor having an array of pixels, and each pixel may include a demodulation circuit having a pin photodiode having an intrinsic layer doped with germanium. In some embodiments, the photosensitive surface of the photodetector of the pixel may have normal incidence (angle of incidence is 0) for receiving light.

[0071] Although the active depth sensing system is depicted as including one receiver and one image sensor, any number of receivers or image sensors may be included in the active depth sensing system. For example, the active depth sensing system may include multiple image sensors for light sensing from different angles. In addition, although the device 1100 is depicted as including one active depth sensing system, the device 1100 may include or may be coupled to additional active depth sensing systems, and the present disclosure is not limited to devices including one active depth sensing system. In some other embodiments, the active depth sensing system may be a structured light system, and the transmitter 1101 and the receiver 1102 may be baseline separated to facilitate performing depth sensing.

[0072] The memory 1106 may be a non-transitory or non-temporary computer-readable medium that stores computer-executable instructions 1108 for performing all or part of one or more device operations. The processor 1104 may be one or more suitable processors capable of executing scripts or instructions of one or more software programs (e.g., instructions 1108) stored in the memory 1106. In some aspects, the processor 1104 may be one or more general-purpose processors that execute instructions 1108 to enable the device 1100 to perform any number of functions or operations. In additional or alternative aspects, the processor 1104 may include an integrated circuit or other hardware to perform functions or operations without the use of software. For example, the TOF system may be a LIDAR system, and the device 1100 may be a device for controlling the navigation of a vehicle (such as a car or UAV). The processor 1104 may execute instructions 1108 to enable the device 1100 to control the navigation of the vehicle (such as speed, steering, acceleration, height, etc.) based on the depth sensing of the active depth sensing system. The device 1100 may also be configured to alert a user (such as a driver or UAV operator) of obstacles or other events based on depth sensing.

[0073] Although in Fig.11 1104, however, the processor 1104, memory 1106, controller 1110, optional display 1114, and optional I / O components 1116 may be coupled to each other in various arrangements. For example, the processor 1104, memory 1106, controller 1110, optional display 1114, and optional I / O components 1116 may be coupled to each other via one or more local buses (not shown for simplicity).

[0074] Display 1114 may be any suitable display or screen that allows user interaction and / or presents items to the user (e.g., a depth map, a preview image of a scene, an alert, etc.). In some aspects, display 1114 may be a touch-sensitive display. In some examples, display 1114 may be a heads-up display or a center console display in an automobile, display 1114 may be a display of a smartphone, digital camera, or other electronic device, or the display may be a display on a user controller of the UAV.

[0075] The I / O component 1116 may be or may include any suitable mechanism, interface, or device for receiving external input and providing output. In some embodiments, the I / O component 1116 may include an interface to receive requests or commands from a user or provide feedback to a user. In some other embodiments, the I / O component 1116 may include an interface to receive feedback about the operation of the device (such as the speed and other measurements of the vehicle). For example, the I / O component 1116 may include, but is not limited to, a graphical user interface, a keyboard, a mouse, a microphone and a speaker, a squeezable frame or border of a handheld device, a physical button, an interface coupled to a communication network of the car, a UAV controller, and the like.

[0076] The controller 1110 may include a signal processor 1112, which may be one or more processors to process measurements provided by the receiver 1102 or to control the operation of the transmitter 1101 and the receiver 1102. In some aspects, the signal processor 1112 may execute instructions from a memory (such as instructions 1108 from the memory 1106 or instructions stored in a separate memory coupled to the signal processor 1112). In other aspects, the signal processor 1112 may include specific hardware for operation. The signal processor 1112 may alternatively or additionally include a combination of specific hardware and the ability to execute software instructions.

[0077] As noted, the image sensor of the active depth sensing system may include one or more photodetectors. Each photodetector may include a photosensitive surface containing germanium to improve the absorption of photons at higher wavelengths (such as wavelengths greater than 1000 nanometers) than a pure silicon photosensitive surface. The operation of the photodetector containing germanium can be similar to the operation of the photodetector that does not contain germanium. For example, a pin photodiode having an intrinsic layer doped with germanium can operate in a manner similar to a pin photodiode having an intrinsic layer undoped with germanium, except that the pin photodiode having an intrinsic layer doped with germanium can have a higher absorption efficiency for photons of specific wavelengths of light (such as wavelengths greater than 1000 nanometers). Compared to a photodiode containing silicon in the intrinsic layer, a pin photodiode having a germanium crystal intrinsic layer has a higher absorption efficiency for photons of light with a wavelength greater than 1400 nanometers.

[0078] Fig.121200 is a flow chart depicting an example operation of an image sensor. The example image sensor includes a pixel including a photodetector having a photosensitive surface including germanium. At 1202, the photosensitive surface of the photodetector receives light. In some embodiments, the light includes reflections of emitted light for an active depth sensing system. For example, the light may include one or more reflections of frequency modulated light having a first wavelength, which is emitted for indirect TOF depth sensing. In some embodiments, the photodetector may include a photodiode, and the photodiode may receive the light at an intrinsic layer (1204). In some embodiments, the intrinsic layer may be a silicon layer doped with germanium. In some other embodiments, the intrinsic layer may be a germanium crystal layer. The intrinsic layer may be located between a p-layer and an n-layer that are not doped with germanium or do not include germanium.

[0079] The photosensitive surface of the photodetector can absorb a photon of light (1206). In some embodiments, the germanium-doped intrinsic layer can absorb the received photon of light (1208). At 1210, the photodetector can generate a current based on the absorbed photon. For example, a photodiode can generate a current (such as described above with reference to Figure 8 As described above, the current can vary depending on the intensity of the received light. If the light includes reflections of frequency modulated emitted light, then the intensity of the received light varies based on the phase of the reflected light received by the pixel.

[0080] In some embodiments, the image sensor may enable one or more sampling circuits (1212) coupled to the photodiode. The enabling may be based on the phase of the emitted light (such as from an indirect TOF emitter). For example, reference back Figure 4 , transistors 404 and 406 can be activated based on the phase of the emission signal 408 or the inverted emission signal 410 (which can be a phase offset of the emission signal 408). The one or more enabled sampling circuits can then generate a voltage indicating a phase difference between one or more reflections of the emission light (as received in the received light) and the emission light from the indirect TOF emitter (1214). For example, if the current from the photodiode is below a threshold, the enabled sampling circuit can generate a low voltage signal. If the current from the photodiode is above a threshold, the enabled sampling circuit can generate a high voltage signal. Whether the current is above or below the threshold can correspond to the phase of the reflection of the emission signal received by the pixel. In this way, the voltage can indicate a phase difference between the reflection of the emission light and the emission light.

[0081] In some embodiments, a device can determine a phase difference between emitted light and a reflection of the emitted light received at a pixel (e.g., at an intrinsic layer of a photodiode) (1216). Determining the phase difference is based on voltages generated by one or more sampling circuits. For example, for a four-phase demodulated pixel, the voltages generated by the four sampling circuits can be compared (such as which voltages are low voltages and which voltages are high voltages). Then, the phase difference can be determined based on the comparison.

[0082] As noted, a device can determine the depth of an object surface relative to a pixel based on phase difference. In some embodiments, the depth can be used to control the operation of the device. For example, the indirect TOF system can be a LIDAR system, and the LIDAR system can be used to control the navigation of a vehicle (such as a car or UAV). In some other embodiments, the depth can be determined to generate a depth map, provide the depth to a user, or provide other suitable applications to the active depth sensing system.

[0083] In the specification, in order to provide a thorough understanding of the present disclosure, many specific details, such as examples of specific components, circuits and processes, have been set forth. As used herein, the term "coupling" refers to being directly connected to or connected through one or more intermediate components or circuits. In addition, in the description and for the purpose of explanation, specific terms are set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that these specific details may not be needed to practice the teachings disclosed herein. In other examples, well-known circuits, systems and devices are shown in block diagram form to avoid obscuring the teachings of the present disclosure. Certain parts of the detailed description are presented according to processes, logic blocks, processing and other symbolic representations of the operation of data bits in computer memory. In the present disclosure, processes, logic blocks, processing, etc. are considered to be self-consistent sequences of steps or instructions that lead to desired results. These steps are steps that require physical manipulation of physical quantities. Typically, although not necessarily, these quantities take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared and otherwise manipulated in a computer system.

[0084] It should be kept in mind, however, that all of these terms and similar terms are associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically noted otherwise, it should be understood that throughout this application, discussions utilizing terms such as "access," "receive," "send," "use," "select," "determine," "normalize," "multiply," "average," "monitor," "compare," "apply," "update," "measure," "derive from," "solve," and the like refer to the actions and processes of a computer system or similar electronic computing device that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system's memories or registers or other such information storage, transmission, or display devices.

[0085] In the accompanying drawings, a single block may be described as performing one or more functions; however, in actual practice, one or more functions performed by the block may be performed in a single component or between multiple components, and / or may be performed using hardware, using software, or using a combination of hardware and software. In order to clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules. Circuits and steps are generally described below according to their functions. Whether this functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the entire system. Technicians can implement the described functions in different ways for each specific application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Moreover, the example systems and devices may include components other than the components shown, including well-known components such as processors and memories.

[0086] Aspects of the present disclosure are applicable to active depth sensing (e.g., TOF ranging) and may be included in or coupled to any suitable electronic device or system (e.g., a security system, a smart phone, a tablet, a laptop, a digital camera, a vehicle, a drone, a virtual reality device, or other device that can utilize depth sensing). Although described with respect to a device having or coupled to a TOF system, aspects of the present disclosure are applicable to devices having any number or type of suitable active depth sensing systems.

[0087] The term "device" is not limited to one or a specific number of physical objects (e.g., a smartphone, a controller, a processing system, etc.). As used herein, a device may be any electronic device having one or more components that may implement at least some portion of the present disclosure. Although the description and examples use the term "device" to describe various aspects of the present disclosure, the term "device" is not limited to a specific configuration, type, or number of objects. In addition, the term "system" is not limited to multiple components or specific embodiments. For example, a system may be implemented on one or more printed circuit boards or other substrates, may have one or more housings, may be one or more objects integrated into another device, and may have movable or static components. Although the description and examples use the term "system" to describe various aspects of the present disclosure, the term "system" is not limited to a specific configuration, type, or number of objects.

[0088] Unless specifically described as being implemented in a particular manner, the techniques described herein may be implemented in hardware, software, firmware, or any combination thereof. Any features described as modules or components may also be implemented together in an integrated logic device, or may be implemented separately as discrete but interoperable logic devices. If implemented in software (e.g., a device that changes the spatial pattern of an included structured light system), the techniques may be implemented at least in part by a non-transitory processor-readable storage medium (e.g., Fig.11 The storage medium includes instructions 1108, which, when executed by the processor 1104 (or the controller 1110 or the signal processor 1112), enable the device 1100 or the deep discovery system to perform one or more of the methods described. The non-transitory processor-readable data storage medium (computer-readable medium) may form part of a computer program product, which may include packaging materials.

[0089] The non-transitory processor-readable storage medium may include random access memory (RAM) (e.g., synchronous dynamic random access memory (SDRAM)), read-only memory (ROM), non-volatile random access memory (NVRAM), electrically erasable programmable read-only memory (EEPROM), flash memory, other known storage media, etc. Additionally or alternatively, the technology may be at least partially implemented by a processor-readable communication medium that carries or communicates code in the form of instructions or data structures and can be accessed, read, and / or executed by a computer or other processor.

[0090] Some of the various illustrative logical blocks, modules, circuits, and instructions described in connection with the embodiments disclosed herein may be executed by one or more processors, such as Fig.11The processor 1104 or signal processor 1112 in the exemplary device 1100 of the present invention. Such a processor may include, but is not limited to, one or more digital signal processors (DSPs), general-purpose microprocessors, application-specific integrated circuits (ASICs), application-specific instruction set processors (ASIPs), field programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. As used herein, the term "processor" may refer to any of the aforementioned structures or any other structure suitable for implementing the technology described herein. In addition, in some aspects, the functions described herein may be provided in a dedicated software module or hardware module configured as described herein. Similarly, the technology may be fully implemented in one or more circuits or logic elements. A general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0091] Although the present disclosure shows illustrative aspects, it should be noted that various changes and modifications may be made herein without departing from the scope of the appended claims. For example, although examples of active depth sensing systems are described in conjunction with light emissions, signals at other frequencies may be employed, such as microwaves, radio frequency signals, sound signals, and the like. In addition, unless otherwise expressly stated, the functions, steps, or actions of the method claims according to the various aspects described herein do not need to be performed in any particular order. Furthermore, although elements may be described or claimed in singular form, plural forms are contemplated unless limitation to the singular form is explicitly stated. Therefore, the present disclosure is not limited to the examples shown, and any means for performing the functions described herein are included in the various aspects of the present disclosure.

Claims

1. A device comprising: An image sensor comprising one or more pixels, wherein each of the one or more pixels comprises a photodetector, wherein the photodetector comprises a photodiode, wherein the photodiode comprises: A p-layer that does not contain germanium; An n-layer that does not contain germanium; a photosensitive intrinsic layer between the p-layer and the n-layer, wherein the photosensitive intrinsic layer comprises germanium and is configured to generate an electric current; an n-well coupled to one of the photosensitive intrinsic layer or the n-layer, wherein the n-well is configured to receive the current; and An emitter field effect transistor is configured to output the current from the n-layer.

2. The device of claim 1 , wherein the photosensitive intrinsic layer comprises at least one of the group consisting of: silicon doped with germanium; and Germanium crystal without silicon.

3. The apparatus of claim 1 , wherein the photodiode is one of the group consisting of: vertical pin photodiode; and Horizontal pin photodiode.

4. The apparatus of claim 1 , wherein the photodiode is configured as: receiving one or more reflections of emitted light having a first wavelength for active depth sensing; absorbing the one or more reflected photons of emitted light by the photosensitive intrinsic layer of the photodiode; and The current is generated based on the absorbed photons. The device of claim 4 , wherein the first wavelength is greater than 1000 nanometers.

6. The device according to claim 4, wherein: Active depth sensing includes indirect time-of-flight TOF depth sensing; Each pixel includes one or more sampling circuits coupled to the photodiode; and Each sampling circuit of the one or more sampling circuits is configured to be enabled at a different phase of the emitted light than at least one other sampling circuit of the one or more sampling circuits.

7. The apparatus of claim 6, wherein each pixel is one of the group consisting of: Two-phase demodulated pixels; Three-phase demodulated pixels; and Four-phase demodulated pixel.

8. The apparatus of claim 7, wherein the image sensor comprises an array of demodulated pixels.

9. The apparatus of claim 8, further comprising an indirect TOF receiver, wherein the indirect TOF receiver comprises the image sensor.

10. The apparatus of claim 9, further comprising an indirect TOF transmitter configured to transmit the emission light having the first wavelength, wherein operation of the one or more sampling circuits is based on a phase of the emission light.

11. The apparatus of claim 10, further comprising one or more processors coupled to the indirect TOF transmitter and the indirect TOF receiver to form an indirect TOF depth sensing system, wherein the one or more processors are configured to control operation of the indirect TOF transmitter and the indirect TOF receiver.

12. The apparatus of claim 11, wherein the indirect TOF depth sensing system is a Light Detection and Ranging (LIDAR) system.

13. The apparatus of claim 12, wherein the LIDAR system is coupled to or included in a vehicle, wherein navigation of the vehicle is based on operation of the LIDAR system. The device of claim 13 , wherein the first wavelength is greater than 1000 nanometers.

15. An operating method, comprising: receiving light at a photosensitive intrinsic layer of a photodiode of a photodetector of a pixel of the image sensor, wherein the photosensitive intrinsic layer comprises germanium and is located between a p-layer that does not comprise germanium and an n-layer that does not comprise germanium; absorbing photons of said light by said photosensitive intrinsic layer; generating an electric current by the photosensitive intrinsic layer based on the absorbed photons; receiving the current at an n-well coupled to one of the photosensitive intrinsic layer or the n-layer; and The current from the n-layer is output by an emitter field effect transistor.

16. The method of claim 15, wherein the photosensitive intrinsic layer comprises at least one of the group consisting of: silicon doped with germanium; and Germanium crystal without silicon.

17. The method of claim 16, wherein the light comprises one or more reflections of emitted light having a first wavelength for active depth sensing.

18. The method of claim 17, wherein: The active depth sensing comprises indirect time-of-flight (TOF) depth sensing; and The emitted light is frequency modulated.

19. The method according to claim 18, further comprising: enabling one or more sampling circuits coupled to the photodiode based on the phase of the emitted light; as well as A voltage is generated by each of the one or more sampling circuits, the voltage being indicative of a phase difference between the one or more reflections of the emitted light and the emitted light.

20. The method according to claim 19, further comprising: determining a phase difference between the emitted light and a reflection of the emitted light received at the photosensitive intrinsic layer of the photodiode based on the voltage generated by the one or more sampling circuits; and Based on the phase difference, a depth of a surface of an object relative to the pixel of the image sensor is determined.

21. The method of claim 20, further comprising emitting the emission light having the first wavelength.

22. The method of claim 21, wherein the first wavelength is greater than 1000 nanometers.

23. The method according to claim 22, further comprising: Based on the depth of the surface of the object relative to the pixel, navigation of a vehicle is controlled.

24. A non-transitory computer-readable medium storing instructions that, when executed by one or more processors of a device, cause the device to: receiving light at a photosensitive intrinsic layer of a photodiode of a photodetector of a pixel of an image sensor of the device, wherein the photosensitive intrinsic layer comprises germanium and is located between a p-layer that does not comprise germanium and an n-layer that does not comprise germanium; absorbing photons of said light by said photosensitive intrinsic layer; generating an electric current based on the absorbed photons by the photosensitive intrinsic layer detector; receiving the current at an n-well coupled to one of the photosensitive intrinsic layer or the n-layer; and The current from the n-layer is output by an emitter field effect transistor.

25. The computer readable medium of claim 24, wherein the photosensitive intrinsic layer comprises at least one of the group consisting of: silicon doped with germanium; and Germanium crystal without silicon.

26. The computer-readable medium of claim 25, wherein execution of the instructions further causes the device to: emitting emission light having a first wavelength for indirect time-of-flight (TOF) depth sensing, wherein the light received at the photosensitive intrinsic layer of the photodiode includes one or more reflections of the emission light; enabling one or more sampling circuits coupled to the photodiode based on the phase of the emitted light; generating, by each of the one or more sampling circuits, a voltage indicative of a phase difference between the one or more reflections of the emitted light and the emitted light; and Based on the voltage generated by the one or more sampling circuits, a phase difference between the emitted light and a reflection of the emitted light is determined.

27. An apparatus comprising: means for receiving light at a photosensitive intrinsic layer of a photodiode of a photodetector of a pixel of an image sensor, wherein the photosensitive intrinsic layer comprises germanium and is located between a p-layer that does not comprise germanium and an n-layer that does not comprise germanium; means for absorbing photons of said light by said photosensitive intrinsic layer; means for generating an electric current based on absorbed photons by the photosensitive intrinsic layer; means for receiving said current at an n-well coupled to one of said photosensitive intrinsic layer or said n-layer; as well as means for outputting said current from said n-layer by an emitter field effect transistor.

28. The device of claim 27, wherein the photosensitive intrinsic layer comprises at least one of the group consisting of: silicon doped with germanium; and Germanium crystal without silicon.

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