Terahertz array detection devices based on InGaAs / AlGaAs

Abstract

The present invention discloses a terahertz array detection device based on InGaAs / AlGaAs, wherein a GaAs buffer layer, an AlGaAs layer and a GaAs buffer layer are sequentially grown on a GaAs substrate. x Ga 1‑x As buffer layer, Al x Ga 1‑x As barrier layer, Si delta-doped bottom layer, Al x Ga 1‑x As isolation layer, In x Ga 1‑x As channel layer, Al x Ga 1‑x As isolation layer, Si delta doping layer, Al x Ga 1‑x As barrier layer, undoped AlAs layer, undoped GaAs layer, Si-doped AlAs barrier layer and Si-doped GaAs cap layer. The source and drain electrodes are in contact with the GaAs buffer layer and the two ends of each barrier layer to form ohmic contacts, and a two-dimensional electron gas channel is formed between the channel layers. Its main feature is that the two-dimensional electron gas formed by InGaAs / AlGaAs has a very high electron mobility and can generate plasma resonance with terahertz waves, thereby enhancing the absorption of terahertz waves and improving the photoelectric conversion efficiency. The advantage of the present invention is that the designed array device can not only achieve a higher response, but also achieve a better uniformity feature. The linear array chip based on this is conducive to large-scale integration and expansion.

Description

Technical Field

[0001] The present invention is a terahertz (THz) detection device based on semiconductor heterojunction high electron mobility transistor technology, specifically a two-dimensional electron gas (2-DEG) formed based on InGaAs / AlGaAs heterojunction. Background Art

[0002] Terahertz radiation (0.1-10 THz) holds great promise in many disciplines, including materials research, safety testing, environmental monitoring, and communications, due to its remarkable properties, including low photon energy, strong penetration, high frequency, and ultrashort pulses. The primary method for utilizing terahertz radiation is terahertz detection technology, which has a significant impact on both basic and applied terahertz research. Room-temperature, high-speed, and highly sensitive terahertz array detectors are fundamental tools for the advancement of terahertz application technology and a key method and component of terahertz scientific research. A high electron mobility transistor (HEMT) is a field-effect transistor with a heterojunction structure, also known as a modulation-doped field-effect transistor or a two-dimensional electron gas field-effect transistor. It utilizes a heterojunction formed by two materials with different band gaps, creating a triangular potential well at the interface. The two-dimensional electron gas in this well acts as a field-effect transistor for channel modulation. Because electrons are concentrated in this heterojunction, the holes and electrons are spatially separated, resulting in high electron mobility. Therefore, the device has the characteristics of large transconductance, high cutoff frequency, low noise, and fast switching speed, and has broad application prospects in microwave amplifiers and power devices.

[0003] In 1993, Dyakonov and Shur first proposed that the nonlinear properties of plasma waves could be used to detect terahertz waves. Terahertz waves excite plasma waves within a channel. The nonlinear properties of the plasma waves and the asymmetric boundary conditions induce a constant voltage, the so-called terahertz response. In 1998, non-resonant detection was first discovered in GaAs high-electron-mobility transistors (HEMTs). Since then, a series of high-electron-mobility transistors and silicon-based field-effect transistors have demonstrated non-resonant, room-temperature, high-sensitivity field-effect self-mixing terahertz wave detectors.

[0004] InGaAs / AlGaAs HEMT is a new type of device. A two-dimensional electron gas is formed in the channel of the HEMT device. From the beginning to the present, all research on HEMT is aimed at improving the electron mobility and surface electron concentration in its channel. Generally, the band gap width of the material is changed by selecting and doping the heterojunction material, and the Fermi level difference of the heterojunction material is changed to improve the electron mobility of the device. Increasing and regulating the electron mobility will greatly improve the performance of the device. GaAs buffer layer, AlGaAs layer and GaAs layer are grown on the GaAs substrate in sequence. xGa 1-x As buffer layer, Al x Ga 1-x As barrier layer, Si delta-doped bottom layer, Al x Ga 1-x As isolation layer, In x Ga 1-x As channel layer, Al x Ga 1-x As isolation layer, Si delta doping layer, Al x Ga 1-x As barrier layer, undoped AlAs layer, undoped GaAs layer, Si-doped AlAs barrier layer and Si-doped GaAs cap layer. In this structure of HEMT, due to the doped AlAs x Ga 1-x The Fermi level of As and In x Ga 1-x The position of the Fermi level of As is different, the electrons will be drawn from Al x Ga 1-x As material side is transferred to the lower In x Ga 1-x On the As material side, electrons in the channel are spatially separated from donor ionized impurities, forming a two-dimensional electron gas within the channel. When the device is exposed to terahertz waves, the two-dimensional electron gas generated by the device itself resonates with the terahertz waves, generating plasma waves. Due to the nonlinear characteristics of the plasma waves, the device can respond in the terahertz band.

[0005] Some new two-dimensional materials have achieved substantial breakthroughs in terahertz detection, such as achieving high current response rates in the terahertz band. However, the instability of two-dimensional materials and the inability to integrate them in wafer form have limited their application in the terahertz band. For these devices to be used in practical equipment and facilities, a stable and uniform response across the array is essential. Summary of the Invention

[0006] The purpose of the present invention is to provide a novel InGaAs / AlGaAs HEMT array device structure to achieve device response in the terahertz band, increase device stability and terahertz response uniformity, and realize the application of terahertz devices in imaging.

[0007] The GaAs / AlGaAs HEMT device structure of the present invention is shown in FIG. Figure 1 As shown, it includes: growing GaAs buffer layer 2, Al x Ga 1-x As buffer layer 3, Alx Ga 1-x As barrier layer 4, Si delta-doped bottom layer 6, Al x Ga 1-x As isolation layer 7, In x Ga 1-x As channel layer 8, Al x Ga 1-x As isolation layer 9, Si delta doping layer 10, Al x Ga 1-x As barrier layer 11, undoped AlAs layer 12, undoped GaAs layer 13, Si-doped AlAs barrier layer 14 and Si-doped GaAs cap layer 15. The source 5 and drain 16 are in contact with the GaAs buffer layer and each barrier layer at both ends to form an ohmic contact, and a two-dimensional electron gas (2-DEG) channel 17 is formed between the channel layers. The source and drain metal electrodes are AuGe / Ni / Au, wherein the thickness of the AuGe alloy is 100-120nm, the thickness of Ni is 20-30nm, the thickness of Au is 200-220nm, the device channel length is 1.5-2μm, and the width is 15-17μm (0.1THz) and 5-6μm (0.3THz). In this structure, the high-mobility 2-DEG generated by the InGaAs / AlGaAs heterojunction acts as a conductive channel with high stability. The thickness of the GaAs buffer layer 2 is 200-210nm, the thickness of the AlAs is 200-30nm, and the thickness of the AuAs is 200-220nm. x Ga 1-x As buffer layer 3 has a thickness of 250-300nm, Al x Ga 1-x As barrier layer 4 has a thickness of 15-20 nm, Si δ doped bottom layer 6, Al x Ga 1-x The thickness of the isolation layer 7 of As is 6-10nm, x Ga 1-x The channel layer 8 of As has a thickness of 5-10 nm, and the Al x Ga 1-x The thickness of the As isolation layer 9 is 6-10 nm, the Si delta doping layer 10, the Al x Ga 1-x The As barrier layer 11 has a thickness of 22-25 nm, the undoped AlAs layer 12 has a thickness of 1.5-2 nm, the undoped GaAs layer 13 has a thickness of 15-20 nm, the Si-doped AlAs barrier layer 14 has a thickness of 1.5-3 nm, and the Si-doped GaAs cap layer 15 has a thickness of 25-30 nm.

[0008] The present invention achieves its objectives by the following method: The two-dimensional electron gas formed by InGaAs / AlGaAs has very high electron mobility and can generate plasma resonance with THz waves, thereby enhancing THz wave absorption and improving THz wave photoelectric conversion efficiency. Therefore, the array device can utilize the coupling effect between THz waves and the 2-DEG in the device channel to generate plasma waves. Due to the nonlinear characteristics of the plasma waves, the device can achieve a response signal in the THz band. Because the material stability of InGaAs / AlGaAs is higher than that of other two-dimensional materials, the THz responsivity of the HEMT device prepared is also relatively stable. At the same time, the unique structural design of the HEMT device can ensure uniformity among the array devices. Because the device response is relatively stable in the THz band, imaging of the device in the THz band can be achieved.

[0009] Another object of the present invention is to provide a method for preparing and designing the above-mentioned InGaAs / AlGaAs HEMT device, the specific steps of which are as follows:

[0010] (1) The above-mentioned layers of materials are grown on a GaAs substrate using the MBE method. The thickness of the GaAs buffer layer 2 is 200-210 nm, and the Al x Ga 1-x As buffer layer 3 has a thickness of 250-300nm, Al x Ga 1-x As barrier layer 4 has a thickness of 15-20 nm, Si δ doped bottom layer 6, Al x Ga 1-x The thickness of the isolation layer 7 of As is 6-10nm, x Ga 1-x The thickness of the As channel layer 8 is 5-10 nm.

[0011] Al x Ga 1-x The thickness of the As isolation layer 9 is 6-10 nm, the Si delta doping layer 10, the Al x Ga 1-x As

[0012] The barrier layer 11 has a thickness of 22-25 nm, the undoped AlAs layer 12 has a thickness of 1.5-2 nm, the undoped GaAs layer 13 has a thickness of 15-20 nm, and the Si-doped AlAs barrier layer 14 has a thickness of

[0013] 1.5-3nm, and the thickness of the Si-doped GaAs cap layer 15 is 25-30nm.

[0014] (2) The cleaning method is to ultrasonically clean the complete 4-inch wafer in acetone and isopropyl alcohol for about 5 minutes each, twice, then ultrasonically clean and rinse with deionized water four to five times, and finally blow dry the cleaned material with a nitrogen gun.

[0015] (3) Use ultraviolet lithography to photoetch the trench, and then use wet etching to etch the trench. The etching depth is 110-130 nm, the etching time is about 28-30 s, and the composition ratio of the etching solution is H3PO4:

[0016] H2O2:H2O=1:1:25, thereby obtaining a two-dimensional electron gas channel.

[0017] (4) Clean the corroded sample using the method of step (2).

[0018] (5) Use ultraviolet lithography to etch out the source and drain ends of the device, and then use electron beam evaporation to evaporate gold. The evaporated metal materials are AuGe / Ni / Au in sequence, with thicknesses of 100-120,

[0019] 20-30, 200-220nm.

[0020] (6) Then use N-methylpyrrolidone (NMP) stripping solution to strip the glass. The method is to put the evaporated material into N-methylpyrrolidone (NMP) stripping solution and heat it in a water bath.

[0021] After about 60 minutes, the metal and the material are automatically separated.

[0022] (7) Annealing is performed in a rapid annealing furnace. Before heating, nitrogen is first turned on for 60-70 seconds to fill the cavity. Then, the temperature is raised to 200-210 degrees Celsius for 15-20 seconds and maintained for 10-15 seconds to preheat. Then, the temperature is raised to 430-450 degrees Celsius for 20-25 seconds and maintained at -430-450 degrees Celsius for 30-35 seconds to complete the annealing. Then, IV test is performed on both ends of the device to confirm that the ohmic contact of the device is good.

[0023] The process steps of the present invention are currently very mature standard processes in China, and the process is relatively simple. Its process parameters are obtained through multiple experiments and are very representative. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a side view of the InGaAs / AlGaAs HEMT array device structure of the present invention.

[0025] Figure 2This is a schematic diagram of the 0.1THz structure of the InGaAs / AlGaAs HEMT array device of the present invention. Figure a shows the overall structure of the antenna, and Figure b shows the fine structure at the channel.

[0026] Figure 3 This is a schematic diagram of the 0.3THz structure of the InGaAs / AlGaAs HEMT array device of the present invention. Figure a shows the overall structure of the antenna, and Figure b shows the fine structure at the channel.

[0027] Figure 4 This is the response current curve of the InGaAs / AlGaAs HEMT array device of the present invention as the bias voltage changes.

[0028] Figure 5 The figure shows the response uniformity of the InGaAs / AlGaAs HEMT array device of the present invention when irradiated with electromagnetic waves at frequencies of 0.1 THz and 0.3 THz.

[0029] Figure 6 is the response time of the InGaAs / AlGaAs HEMT array device of the present invention at 0.1 THz.

[0030] Figure 7 is the response time of the InGaAs / AlGaAs HEMT array device of the present invention at 0.3 THz. DETAILED DESCRIPTION

[0031] Next, we will focus on the antenna structure design of the present invention and some applications in terahertz imaging. Through the above device preparation method, we have obtained an array device, whose side structure is as follows Figure 1 To ensure the uniformity and responsiveness of the array device, we simulated and designed a new grid antenna structure with resonant frequencies of 0.1 THz and 0.3 THz. Figure 2 a shows the overall structure of the 0.1 THz antenna. Figure 2 b shows the fine structure of the antenna channel, where the width of L1 is 345-350μm, the width of L2 is 237-240μm, the width of D1 is 15-20μm, the width of D2 is 11-15μm, the width of D3 is 25-30μm, and the width of D4 is 24-30μm. Figure 3 a shows the overall structure of the 0.3 THz antenna. Figure 3b shows the fine structure at the channel, where the width of J1 is 69-70μm, the width of J2 is 180-185μm, the width of I1 is 10-12μm, the width of I2 is 5-7μm, the width of I3 is 11-15μm, and the width of I4 is 25-30μm. A microwave generator is used to generate low-frequency microwaves, which generate electromagnetic waves of 0.1 and 0.3THz through a multiplication link. The optical response is recorded by an oscilloscope after a lock-in amplifier (LIA) and a low-noise voltage preamplifier. The specific operation is to use the pulse signal modulation frequency of the microwave source as the reference signal source of the phase-locked amplifier and the oscilloscope, and at the same time connect the detector photoelectric signal amplified by the preamplifier to the input port of the phase-locked amplifier. The output signal is the signal after phase-locking and re-amplification. The optical response at two frequencies changes with the bias voltage as shown in the figure. Figure 4 a (0.1 THz) and b (0.3 THz), where the distance between the light source and the array detector is about 50 cm. Figure 4 The spacing between the channels is 2μm, and devices with different channel widths, D1 (15μm, 17μm, 20μm) and I2 (5μm, 6μm, 7μm), were prepared. In order to verify the uniformity of the devices we designed, 12 devices with the same channel width were randomly selected from the same batch and tested using the same method for the optical response of the devices. Figure 5 The array devices shown exhibit good uniformity at both 0.1 THz and 0.3 THz, with the photoresponse error between devices remaining within 10%. Figure 6 Figure 2 shows the response time of a 0.1THz array terahertz detector at zero bias (the inset shows the falling edge), which is typically calculated as the amount of time required for the optical response of a single pulse to increase from 10% to 90% or decrease from 90% to 10%. The device turn-on time is approximately 0.9μs and the turn-off time is approximately 0.7μs. The device response time is fast enough for use in high-speed devices. Figure 7 This is a time-dependent response diagram of a 0.3 THz array terahertz detector at zero bias (the inset shows the falling edge). The device turns on in approximately 1 μs and turns off in approximately 0.8 μs. The terahertz response of our device is relatively stable, enabling long-term terahertz data acquisition and terahertz imaging.

Claims

1. A terahertz array detection device based on InGaAs / AlGaAs, comprising a GaAs substrate (1), a GaAs buffer layer (2), an Al x Ga 1-x As buffer layer (3), Al x Ga 1-x As barrier layer (4), Si delta doped bottom layer (6), Al x Ga 1-x As isolation layer (7), In x Ga 1-x As channel layer (8), Al x Ga 1-x As isolation layer (9), Si delta doping layer (10), Al x Ga 1-x As barrier layer (11), undoped AlAs layer (12), undoped GaAs layer (13), Si-doped AlAs barrier layer (14) and Si-doped GaAs cap layer (15); characterized in that The structure of the terahertz array detection device is as follows: A GaAs buffer layer (2), an Al x Ga 1-x As buffer layer (3), Al x Ga 1-x As barrier layer (4), Si delta doped bottom layer (6), Al x Ga 1-x As isolation layer (7), In x Ga 1-x As channel layer (8), Al x Ga 1-x As isolation layer (9), Si delta doping layer (10), Al x Ga 1-x As barrier layer (11), undoped AlAs layer (12), undoped GaAs layer (13), Si-doped AlAs barrier layer (14) and Si-doped GaAs cap layer (15); source electrode (5) and drain electrode (16) are respectively located at the GaAs buffer layer and at both ends of each barrier layer to form ohmic contacts, and a two-dimensional electron gas channel is formed between the channel layers; The thickness of the GaAs buffer layer (2) is 200-210nm, the Al x Ga 1-x The As buffer layer (3) has a thickness of 250-300 nm; The Al x Ga 1-x The As barrier layer (4) has a thickness of 15-20 nm; The Si delta doped bottom layer (6) and Al x Ga 1-x The thickness of the As isolation layer (7) is 6-10 nm; The In x Ga 1-x The thickness of the As channel layer (8) is 5-10 nm; The Al x Ga 1-x The thickness of the As isolation layer (9) is 6-10 nm; The Si delta doping layer (10) and the Al x Ga 1-x The thickness of the As barrier layer (11) is 22-25 nm; The undoped AlAs layer (12) has a thickness of 1.5-2 nm; The undoped GaAs layer (13) has a thickness of 15-20 nm; The Si-doped AlAs barrier layer (14) has a thickness of 1.5-3 nm; The Si-doped GaAs cap layer (15) has a thickness of 25-30 nm.

2. The InGaAs / AlGaAs-based terahertz array detection device according to claim 1, characterized in that: The terahertz array detection device adopts molecular beam epitaxy technology to sequentially grow a buffer layer and a barrier layer on a GaAs substrate, the source and the drain contact the barrier layer and the buffer layer to form an ohmic contact, and a two-dimensional electron gas (17) is formed between the channel layers. The source and drain metal electrodes are AuGe / Ni / Au, wherein the AuGe alloy thickness is 100-120nm, the Ni thickness is 20-30nm, and the Au thickness is 200-220nm. The device channel length is 1.5-2μm, and the width is 15-17μm when the device frequency is 0.1THz, and the width is 5-6μm when the device frequency is 0.3THz.

3. The InGaAs / AlGaAs-based terahertz array detection device according to claim 1, characterized in that: The source (5) and drain (16) are a grid antenna structure. In the 0.1 THz grid antenna structure, the width of L1 is 345-350 μm, the width of L2 is 237-240 μm, the width of D1 is 15-20 μm, the width of D2 is 11-15 μm, the width of D3 is 25-30 μm, and the width of D4 is 24-30 μm. In the 0.3 THz grid antenna structure, the width of J1 is 69-70 μm, the width of J2 is 180-185 μm, the width of I1 is 10-12 μm, the width of I2 is 5-7 μm, the width of I3 is 11-15 μm, and the width of I4 is 25-30 μm.

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