Avalanche photodiode excess noise factor measurement system and measurement method

Abstract

The disclosure provides an avalanche photodetector excess noise factor measurement system and a measurement method. The avalanche photodetector excess noise factor measurement system comprises a carrier device, a light source, a spectrum analyzer, a biasing device, a source voltage meter and a high-frequency probe; the carrier device is used for placing a device to be measured, the device to be measured comprising an avalanche photodetector chip; the light source is used for outputting constant light to the avalanche photodetector chip for noise testing; and the avalanche photodetector chip is connected with the biasing device, the biasing device is connected with the source voltage meter based on a direct current channel, and the biasing device is connected with the spectrum analyzer based on an alternating current channel through the high-frequency probe to form a noise testing link.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of testing of semiconductor optoelectronic devices, and more particularly to a system and method for measuring excess noise factor of avalanche photodetector. BACKGROUND

[0002] The existing test and measurement of excess factor of avalanche photodetector requires external low-noise amplifiers and external calibration links, which is harsh on noise testing instruments and complex for the test system. The external low-noise amplifier link in noise testing has certain influence on the avalanche photodetector noise test, which brings relatively large error to the excess noise test.

[0003] For example, the following three ways, one is to measure the electron, hole collision ionization rate α, β of APD respectively, and then take the ratio. This method is more cumbersome, and two different wavelengths of stable light source must be used to meet the single carrier injection multiplication region condition. For example, for InP multiplication layer APD, two light sources of 780 nm and 1300 nm are required to ensure pure electron and hole injection, and then the gain under the two injection conditions is measured respectively, and then the electron collision ionization rate α and the hole collision ionization rate β are fitted according to the theoretical formula, and finally the k value is obtained. This test method is complicated in condition and large in calculation. The second is the phase-locked measurement method, which is based on the phase-locked amplifier. The photocurrent is converted into a voltage signal through a transimpedance amplifier, and is input into the LIA in two ways. One is used to calculate the gain, and the other is used to calculate the noise power. Compared with the standard PIN device, the APD excess noise factor is obtained by substituting the formula. This method uses more instruments and takes a long time to test. SUMMARY

[0004] In view of the above problems, the present disclosure provides a system and method for measuring excess noise factor of avalanche photodetector.

[0005] According to a first aspect of the present disclosure, a system for measuring excess noise factor of avalanche photodetector is provided, comprising: a carrier device, a light source, a spectrum analyzer, a biasing device, a source voltage meter and a high-frequency probe; the carrier device is used to place a device to be tested, the device to be tested comprising an avalanche photodetector chip; the light source is used to output stable light to the avalanche photodetector chip for noise testing; and the avalanche photodetector chip is connected with the biasing device, the biasing device is connected with the source voltage meter based on a direct current path, and the biasing device is connected with the spectrum analyzer based on an alternating current path through the high-frequency probe, so as to form a noise test link.

[0006] According to an embodiment of the present disclosure, the AC channel comprises a high-frequency transmission line.

[0007] According to an embodiment of the present disclosure, the high-frequency probe comprises a radio frequency high-speed probe.

[0008] According to an embodiment of the present disclosure, the light source comprises a laser.

[0009] A second aspect of the present disclosure provides a measurement method applied to the system of the first aspect, the method comprising: configuring a spectrum analyzer; connecting an avalanche photodetector chip on a carrier device to a biasing device, the biasing device being connected to a source voltage meter based on a DC channel, the biasing device being connected to the spectrum analyzer based on an AC channel through a high-frequency probe to obtain a noise test link; configuring a working current of a light source to an output power lower than a threshold value, and outputting steady light to the avalanche photodetector chip through an optical fiber; determining a voltage value of a one-gain voltage point of the avalanche photodetector chip through responsivity test of the avalanche photodetector chip based on the noise test link; selecting a plurality of target voltage values between the voltage value of the one-gain voltage point and a voltage value of a breakdown voltage point, and determining excess noise power spectral density and gain values of the avalanche photodetector chip at different target voltage values in light and no-light states respectively; and determining an excess noise factor and a K value representing the excess noise factor according to the excess noise power spectral density and the gain values.

[0010] According to an embodiment of the present disclosure, the configuring the spectrum analyzer comprises one or more of frequency configuration, scan configuration, data processing configuration, and data reading configuration.

[0011] According to an embodiment of the present disclosure, the configuring the spectrum analyzer comprises configuring a center frequency as 50 megahertz and a resolution bandwidth as 1 hertz.

[0012] According to an embodiment of the present disclosure, the method further comprises: after the configuring the spectrum analyzer, performing self-calibration on the spectrum analyzer.

[0013] According to an embodiment of the present disclosure, the method further comprises: determining the excess noise power spectral density of the avalanche photodetector chip at the voltage value of the one-gain voltage point.

[0014] According to an embodiment of the present disclosure, the selecting a plurality of target voltage values between the voltage value of the one-time gain voltage point and the voltage value of the breakdown voltage point, determining the excess noise power spectral density and the gain value of the avalanche photodetector chip at different target voltage values in the light state and the dark state respectively, comprises: determining the dark current value, the photocurrent value, the dark noise power and the light noise power of the avalanche photodetector chip at different target voltage values in the light state and the dark state respectively; and determining the excess noise power spectral density and the gain value according to the dark current value, the photocurrent value, the dark noise power and the light noise power. BRIEF DESCRIPTION OF DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0016] Figure 1 A schematic diagram of an avalanche photodetector excess noise factor measurement system according to an embodiment of the present disclosure is shown schematically.

[0017] Figure 2 A flowchart of an avalanche photodetector excess noise factor measurement method according to an embodiment of the present disclosure is shown schematically. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is intended to provide a thorough understanding of the present disclosure. The following description, given together with the accompanying drawings, is intended to provide a thorough understanding of the present disclosure. However, it is apparent that one or more embodiments can be implemented without the specific details, as is apparent to those skilled in the art. Furthermore, in the following description, descriptions of well-known structures and techniques have been omitted to avoid unnecessarily obscuring the concept of the present disclosure.

[0019] The terms used herein are used only to describe specific embodiments, and are not intended to limit the present disclosure. The terms "include", "comprise" and the like used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0020] All terms used herein, including technical and scientific terms, have meanings commonly understood by one of ordinary skill in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the specification, and should not be interpreted in an idealized or overly formal manner.

[0021] In the case of using expressions similar to "at least one of A, B, and C", it will be understood that the meaning is that "only A", "only B", "only C", "at least one of A and B", "at least one of A and C", "at least one of B and C", "at least one of A, B, and C", "at least one of A, B, and C, and the like are included.

[0022] Figure 1 A schematic diagram of an avalanche photodetector excess noise factor measurement system according to an embodiment of the present disclosure is schematically shown.

[0023] Referring to Figure 1 The avalanche photodetector excess noise factor measurement system 100 provided by the embodiment of the present disclosure comprises a carrier device, a light source, a spectrum analyzer, a biasing device, a source voltage meter, and a high-frequency probe. The carrier device is used to place a device to be tested, and the device to be tested comprises an avalanche photodetector chip. The light source is used to output constant light to the avalanche photodetector chip for noise testing. The avalanche photodetector chip is connected to the biasing device. The biasing device is connected to the source voltage meter based on a direct current channel. The biasing device is connected to the spectrum analyzer based on an alternating current channel through the high-frequency probe, so as to form a noise testing link.

[0024] The alternating current channel can comprise a high-frequency transmission line. That is, the alternating current channel connection adopts a high-frequency transmission line.

[0025] The high-frequency probe can comprise a radio frequency high-speed probe. That is, a radio frequency high-speed probe is adopted as the high-frequency probe.

[0026] The light source can comprise a laser. That is, a laser is adopted as the light source. Other constant light sources can also be included. By testing the excess noise factor of the avalanche photodetector without an external low-noise amplifier link through the use of a laser and other constant light sources, the testing result is more accurate.

[0027] The avalanche photodetector excess noise factor measurement system provided by the embodiment does not need an external low-noise amplifier, and can reduce the noise error caused by the amplifier, that is, the error influence of the noise introduced by the external amplifier link on the noise testing result of the avalanche photodetector is reduced.

[0028] The system simplifies the testing instrument, the testing link is clear, and the testing result is reliable.

[0029] By Figure 2 The avalanche photodetector excess noise factor measurement method of the disclosed embodiment is described in detail.

[0030] Figure 2 A flowchart of an avalanche photodetector excess noise factor measurement method according to an embodiment of the present disclosure is schematically shown. As Figure 2As shown, the embodiment includes operation S210 to operation S260.

[0031] In operation S210, the spectrum analyzer is configured.

[0032] In operation S220, the avalanche photodetector chip on the carrier device is connected to the bias-tee, the bias-tee is connected to the source meter through a DC channel, and the bias-tee is connected to the spectrum analyzer through an AC channel to obtain a noise test link.

[0033] For example, the avalanche photodetector chip is connected to the bias-tee on an optical platform. For example, the avalanche photodetector chip is placed on a constant-temperature TEC platform.

[0034] In operation S230, the operating current of the light source is configured to output power below the threshold value, and the avalanche photodetector chip is outputted with stable light through an optical fiber.

[0035] For example, the laser is biased below the threshold value, a fixed output power is selected, and light is incident on the active region of the avalanche photodetector chip through an optical fiber.

[0036] By biasing the laser below the threshold value, the laser cannot reach the lasing state, thereby outputting relatively weak stable light with low noise.

[0037] It can be understood that the laser in the normal lasing state has relative intensity noise RIN, and the detection of the laser emitted by the detector also introduces light source noise, which is difficult to distinguish in the signal measurement system after being mixed with the noise generated by the detector itself.

[0038] In operation S240, the voltage value of the multiplication gain voltage point of the avalanche photodetector chip is determined by testing the responsivity of the avalanche photodetector chip through the noise test link.

[0039] In operation S250, a plurality of target voltage values are selected between the voltage value of the multiplication gain voltage point and the voltage value of the breakdown voltage point, and the excess noise power spectral density and the gain value of the avalanche photodetector chip at different target voltage values are determined in the light state and the dark state, respectively.

[0040] A plurality of target voltage values can be selected between the voltage value of the multiplication gain voltage point and the voltage value of the breakdown voltage point, and the excess noise power spectral density and the gain value are measured in turn.

[0041] For example, the source meter provides different biases between the voltage value of the multiplication gain voltage point and the voltage value of the breakdown voltage point to the avalanche photodetector chip, and the noise power is measured in the light state and the dark state, respectively. The relationship between the noise power and the excess noise power spectral density is The gain of the avalanche photodetector chip at different voltage values is The excess noise factor at different voltages is

[0042] In operation S260, the excess noise factor and the K value for representing the excess noise factor are determined according to the excess noise power spectral density and the gain value.

[0043] The excess noise factor is calculated according to the excess noise power spectral density, and the K value for representing the excess noise factor is calculated according to the relationship between the gain value and the excess noise factor.

[0044] The avalanche photodetector is an active photodetector device that amplifies the photocurrent through internal gain. Compared with the PIN photodiode, the avalanche photodetector (APD) has a wider application in high-sensitivity low-power signal measurement due to its internal gain mechanism and high sensitivity. A thin p-type layer is added between the i-type absorption zone and the n+ contact layer of the avalanche photodetector. This newly added p-type layer is also a high-field region. When incident light enters the device and generates photo-generated carriers, the photo-generated electrons or holes are accelerated to obtain high enough energy in the high-field region, and collide with bound electrons in the valence band to produce ionization. New carriers also continue to collide and ionize under the action of high electric field, producing the effect of photocurrent multiplication. This carrier multiplication phenomenon is called avalanche effect.

[0045] However, collision ionization is random, which leads to instability of gain. Therefore, a physical quantity, i.e., the excess noise factor, is introduced to represent this gain instability, which is defined as the ratio between the standard deviation of gain and the root mean square The excess noise power spectral density is where F(M) is the excess noise factor. Under the condition of uniform electric field, the local field model of McIntyre shows that the excess noise factor can be expressed as the ratio of the gain of the detector < M>and the ratio k of the ionization coefficients of electrons and holes. The smaller the value of k, the lower the F. The value of k is generally used internationally to measure the excess noise of APD. Quantifying the excess noise factor has great significance for evaluating the performance of APD and better application.

[0046] Determining a multiplication gain voltage point according to the responsivity is more accurate, which is conducive to making the quantified excess noise factor more accurate.

[0047] The light source can use a laser. For example, the laser is biased below the threshold current for noise testing.

[0048] The avalanche photodetector excess noise factor measurement method provided by the embodiment does not need an external low-noise amplifier, can weaken the noise error caused by the amplifier, and reduces the error influence of the noise introduced by the external amplifier link on the avalanche photodetector noise test result.

[0049] The spectrum analyzer is configured, including one or more of frequency configuration, scan configuration, data processing configuration, and data reading configuration.

[0050] For example, the spectrum analyzer tests the frequency configuration, and the spectrum analyzer scans the configuration.

[0051] For example, the frequency configuration is Span ceter (50Mhz)-Range (1Khz), the scan configuration is Res Bw manual (1.0Hz) sweep time (auto), the data processing configuration is mkrfuc-band power (density)-function scan range all, and the data reading configuration is Trace1Mode (Clear Write)-Detector Type (Average)-Smoothing (2%)-Count (2)-linear.

[0052] The spectrum analyzer is configured, including configuring the center frequency as 50 megahertz and the resolution bandwidth as 1 hertz.

[0053] It can be understood that the center frequency, the resolution bandwidth (Res Bw), the scan time (sweep time), and the like of the spectrum analyzer are configured. For example, the center frequency is configured as 50Mhz, the scan frequency range is 1khz (the scan range can be appropriately widened to make the reading stable and repeatable), the resolution bandwidth is configured as 1.0Hz, the scan time is auto, and the spectrum analyzer data reading mode is configured as ClearWrite. The spectrum analyzer reaches the highest power sensitivity, so that the change of the noise can be distinguished to the maximum extent.

[0054] The avalanche photodetector excess noise factor measurement method further includes that after the spectrum analyzer is configured, the spectrum analyzer is self-calibrated.

[0055] It can be understood that after the spectrum analyzer is set and calibrated. The spectrum analyzer is calibrated in the way, without an external noise source calibration circuit, so that the noise test link complexity can be reduced.

[0056] The avalanche photodetector excess noise factor measurement method further includes that the excess noise power spectral density of the avalanche photodetector chip is determined at a voltage value of a gain voltage point.

[0057] For example, by testing the responsivity of the avalanche photodetector chip, a voltage value at which a multiplication gain voltage point of the device is selected, at which voltage the excess noise power spectral density is measured.

[0058] According to the obtained excess noise power spectral density, the excess noise factor can be calculated.

[0059] By testing the responsivity of the avalanche photodetector chip, the voltage value at which the avalanche photodetector chip starts to have gain can be accurately determined, at which voltage the gain in the avalanche photodetector chip is equal to 1, and the ratio F is equal to 1, and the excess noise formula is obtained

[0060] A plurality of target voltage values are selected between the voltage value at the multiplication gain voltage point and the voltage value at the breakdown voltage point, and the excess noise power spectral density and the gain value of the avalanche photodetector chip at different target voltage values are determined in light and dark states, respectively, including: determining the dark current value, the photocurrent value, the dark noise power and the light noise power of the avalanche photodetector chip at different target voltage values in light and dark states, respectively; and determining the excess noise power spectral density and the gain value according to the dark current value, the photocurrent value, the dark noise power and the light noise power.

[0061] In order to better understand the present disclosure, the content of the present disclosure is further described below in combination with embodiments, but the present disclosure is not limited only to the following embodiments.

[0062] For example, (1) Spectrum setting - self calibration. (2) Frequency setting - Span ceter (50Mhz) - Range (1Khz). (3) Sweep setting - Res Bw manual (1.0Hz) - sweep time (auto). (4) Data processing setting - mkrfuc - band power (density) - function scan range all. (5) Data read setting - Trace1 Mode (ClearWrite) - Detector Type (Average) - Smoothing (2%) - Count (2) - linear.

[0063] (6) Place the InAlAs-APD chip on the optical platform, connect through the Bias-tee, connect the source voltage table through the direct current channel, and connect the spectrum analyzer through the radio frequency high-speed probe through the alternating current channel.

[0064] (7) Bias the laser below the threshold current, and the laser output light is about 18uw.

[0065] (8) After the response calculation, the voltage value of the InAlAs-APD multiplication gain point is selected as 10.6V. The corresponding dark current, photocurrent, dark noise power and light noise power are measured under light and no light conditions, and substituted into the formula

[0066] Some voltage values are selected between the voltage of the multiplication gain point 10.6V and the breakdown voltage 27.1V, and the dark current, photocurrent, dark noise power and light noise power are measured respectively, which are substituted into the formula The excess noise factors at different voltages are

[0067] The noise power is measured by the spectrometer under the same voltage, and the average value is taken by repeating 3-5 times.

[0068] According to The k value is calculated.

[0069] For example, (1) the spectrum analyzer is set to self-calibration. (2) The frequency is set to Span center (50Mhz)-Range (1Mhz). (3) The scanning is set to Res Bw manual (1.0Hz)-sweep time (auto). (4) The data processing is set to mkrfuc-band power (density)-function scanning range all. (5) The data reading is set to Trace1 Mode (ClearWrite)-Detector Type (Average)-Smoothing (2%)-Count (2)-linear.

[0070] (6) The Si-APD chip is placed on the optical platform and connected through the Bias-tee, the direct current path is connected to the source voltage table, and the alternating current path is connected to the spectrum analyzer through the radio frequency high-speed probe; the dark condition is measured (Si absorbs visible light).

[0071] (7) The laser is biased below the threshold current, and the laser output light is about 18uw.

[0072] (8) After the response test, the voltage value of the Si-APD multiplication gain point is selected as 16.0V. The corresponding dark current, photocurrent, dark noise power and light noise power are measured under light and no light conditions, and substituted into the formula

[0073] Some voltage values are selected between the voltage of the multiplication gain point 16.0V and the breakdown voltage 132.0V, and the dark current, photocurrent, dark noise power and light noise power are measured respectively, which are substituted into the formula

[0074] The excess noise factor at different voltages is

[0075] The noise power is measured by the spectrum analyzer at the same voltage, and the average value is taken for 3-5 times.

[0076] According to The k value is calculated.

[0077] Those skilled in the art can understand that the features described in various embodiments and / or claims of the present disclosure can be combined or / and combined, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, the features described in various embodiments and / or claims of the present disclosure can be combined and / or combined in various combinations without departing from the spirit and teachings of the present disclosure. All these combinations and / or combinations fall within the scope of the present disclosure.

[0078] The above describes the embodiments of the present disclosure. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. Although each embodiment is described above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various alternatives and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for measuring the excess noise factor of an avalanche photodetector, comprising an excess noise factor measurement system for an avalanche photodetector, the system comprising: The device includes a carrier, a light source, a spectrum analyzer, a bias converter, a source voltage gauge, and a high-frequency probe. The carrier device is used to place the device under test, which includes an avalanche photodetector chip. The light source is used to output steady light to the avalanche photodetector chip for noise testing; and The avalanche photodetector chip is connected to the bias device, which is connected to the source voltage meter via a DC path. The bias device is also connected to the spectrum analyzer via the high-frequency probe via an AC path to form a noise test link. The method includes: Configure the spectrum analyzer; The avalanche photodetector chip located on the carrying device is connected to a bias device. The bias device is connected to the source voltage gauge via a DC path. The bias device is connected to the spectrum analyzer via a high-frequency probe via an AC path to obtain a noise test link. The operating current of the light source is configured to be below the output power threshold, and steady light is output to the avalanche photodetector chip through an optical fiber; The voltage value at the one-gain voltage point of the avalanche photodetector chip is determined by testing the responsivity of the avalanche photodetector chip through the noise test link. Multiple target voltage values ​​are selected between the voltage value at the gain voltage point and the voltage value at the breakdown voltage point. The excess noise power spectral density and gain value of the avalanche photodetector chip at different target voltage values ​​are determined under both illuminated and dark conditions. Based on the excess noise power spectral density and the gain value, the excess noise factor and the K value used to represent the excess noise factor are determined.

2. The method according to claim 1, wherein, The communication path includes a high-frequency transmission line.

3. The method according to claim 1, wherein, The high-frequency probe includes: a radio frequency high-speed probe.

4. The method according to claim 1, wherein, The light source includes: a laser.

5. The method according to claim 1, wherein, The configuration of the spectrum analyzer includes: One or more of the following: frequency configuration, scanning configuration, data processing configuration, and data reading configuration.

6. The method according to claim 1, wherein, The configuration of the spectrum analyzer includes: Configure the center frequency to 50 MHz and the resolution bandwidth to 1 Hz.

7. The method according to claim 1, further comprising: After configuring the spectrum analyzer, the spectrum analyzer is then self-calibrated.

8. The method according to claim 1, further comprising: At the voltage value of the one-gain voltage point, the excess noise power spectral density of the avalanche photodetector chip is determined.

9. The method according to claim 1, wherein, The process of selecting multiple target voltage values ​​between the voltage value at the gain voltage point and the voltage value at the breakdown voltage point, and determining the excess noise power spectral density and gain value of the avalanche photodetector chip at different target voltage values ​​under both illuminated and dark conditions, includes: The dark current, photocurrent, dark noise power, and optical noise power of the avalanche photodetector chip under different target voltage values ​​were determined, both in the presence of light and in the absence of light. The excess noise power spectral density and gain value are determined based on the dark current value, the photocurrent value, the dark noise power, and the photonoise power.

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