A Low Dark Current InAs / GaSb Type II Superlattice Infrared Detector

Abstract

This invention belongs to the field of semiconductor infrared detector technology and discloses a low dark current InAs / GaSb type II superlattice infrared detector. The detector structure includes a GaSb substrate, a GaSb buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, a hole barrier layer, an upper contact layer, a capping layer, a passivation layer, and electrodes. The absorption layer is an unintentionally doped InAs / GaSb type II superlattice absorption layer. Through the dual-barrier structure design of the electron and hole barrier layers, diffusion current, generation-recombination current, and tunneling current are effectively suppressed. By introducing an InSb interface layer into the absorption layer, strain balance of the entire superlattice is achieved, reducing the interface state density, increasing minority carrier lifetime, and reducing SRH recombination-related dark current from the source.

Description

Technical Field

[0001] This invention relates to the field of semiconductor infrared detector technology, and more particularly to an InAs / GaSb type II superlattice infrared detector with low dark current. Background Technology

[0002] InAs / GaSb type II superlattice infrared detectors have broad application prospects in the mid-wave to long-wave infrared detection field due to their advantages such as flexible and tunable band structure, high quantum efficiency, and good material homogeneity. Continuous tuning of the detection wavelength can be achieved by adjusting the thickness of each layer in the superlattice rather than changing the material composition. However, InAs / GaSb type II superlattice infrared detectors have long faced the technical bottleneck of large dark current. Dark current mainly originates from two parts: bulk dark current (including diffusion current, generation-recombination current, and tunneling current) and surface leakage current, which severely restricts the signal-to-noise ratio and detectivity of the detector.

[0003] InAs / GaSb type II superlattices possess a type II gap-broken band arrangement, with electrons and holes spatially separated within the InAs and GaSb layers, respectively. However, the interfaces exhibit various atomic bonding configurations (such as In-Sb and Ga-As), introducing a rich array of interface states. The interface quality directly determines the crystal quality, carrier transport properties, and dark current level of the superlattice material. In existing technologies, the introduction of barrier structures has proven to be an effective method for suppressing dark current; however, further reducing dark current while maintaining quantum efficiency, especially through breakthroughs in interface engineering, remains a critical technical challenge in this field. Summary of the Invention

[0004] The purpose of this invention is to provide an InAs / GaSb type II superlattice infrared detector with low dark current, thereby solving the problem of large dark current in existing InAs / GaSb type II superlattice infrared detectors.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a low dark current InAs / GaSb type II superlattice infrared detector, which comprises, from bottom to top: a GaSb substrate, a GaSb buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, a hole barrier layer, an upper contact layer, and a capping layer. The low dark current InAs / GaSb type II superlattice infrared detector also includes a passivation layer and electrodes; The lower contact layer is an n-type InAs / GaSb type II superlattice lower contact layer; the electron barrier layer is an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice electron barrier layer; the absorption layer is an unintentionally doped InAs / GaSb type II superlattice absorption layer; the hole barrier layer is an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice hole barrier layer; and the upper contact layer is a p-type InAs / GaSb type II superlattice upper contact layer.

[0006] Preferably, the absorption layer includes a mid-wave infrared absorption layer and / or a long-wave infrared absorption layer; the total thickness of the absorption layer is 1.5~3μm.

[0007] Preferably, the superlattice period of the mid-wave infrared absorption layer is composed of 8~10ML InAs / 1ML InSb / 8~10ML GaSb.

[0008] Preferably, the superlattice period of the long-wave infrared absorption layer is composed of 12~15ML InAs / 1ML InSb / 6~8ML GaSb.

[0009] Preferably, the parameters of the GaSb buffer layer include: a thickness of 0.5~1.0 μm, p-type doping with Be, and a doping concentration of 1×10⁻⁶. 16 ~5×10 16 cm -3 .

[0010] Preferably, the parameters of the lower contact layer include: a superlattice period consisting of 8 mL InAs / 8 mL GaSb, a total thickness of 0.5~1 μm, and n-type doping with Si at a doping concentration of 1×10⁻⁶. 18 ~3×10 18 cm -3 .

[0011] Preferably, the parameters of the upper contact layer include: a superlattice period consisting of 8 mL InAs / 8 mL GaSb, a total thickness of 0.3~0.8 μm, and p-type doping using Be with a doping concentration of 1×10⁻⁶. 18 ~3×10 18 cm -3 .

[0012] Preferably, the parameters of the electronic barrier layer include: the superlattice period is composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, and the total thickness is 100~300nm.

[0013] Preferably, the parameters of the hole barrier layer include: the superlattice period is composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, and the total thickness is 100~200nm.

[0014] Preferably, the capping layer is an unintentionally doped InAs layer with a thickness of 5-20 nm; the passivation layer is an Al2O3 layer with a thickness of 50-200 nm; the electrode includes an upper electrode and a lower electrode, the upper electrode being disposed on the capping layer and the lower electrode being disposed on the lower contact layer; the electrode is a Ti / Pt / Au metal layer.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: (1) This invention effectively suppresses diffusion current, generation-recombination current, and tunneling current through a dual-barrier structure design with an electron barrier layer and a hole barrier layer. Simulation results show that the dark current density of the device can be as low as 4.2 × 10⁻⁶ under a bias voltage of 77 K and -0.5 V. -7 A / cm 2 .

[0016] (2) By introducing an InSb interface layer into the absorption layer, the present invention achieves overall strain balance of the superlattice, reduces the interface state density, improves minority carrier lifetime, and reduces the dark current associated with SRH recombination from the source.

[0017] (3) The present invention effectively suppresses the surface leakage current of the mesa sidewall through the Al2O3 passivation layer, and further reduces the total dark current of the device.

[0018] (4) The present invention uses molecular beam epitaxy technology for growth, which is compatible with existing III-V semiconductor process lines and is suitable for large-scale production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0020] Figure 1 This is a schematic diagram of the structure of the low dark current InAs / GaSb type II superlattice infrared detector of the present invention. Figure 2 This is a schematic diagram of the structure of a single superlattice period of the absorption layer in the low dark current InAs / GaSb type II superlattice infrared detector of the present invention. Wherein, 1 is the GaSb substrate, 2 is the GaSb buffer layer, 3 is the lower contact layer, 4 is the electron barrier layer, 5 is the absorption layer, 51 is the InAs layer, 52 is the InSb layer, 53 is the GaSb layer, 6 is the hole barrier layer, 7 is the upper contact layer, 8 is the capping layer, 9 is the passivation layer, 10 is the upper electrode, and 11 is the lower electrode. Detailed Implementation

[0021] This invention provides a low dark current InAs / GaSb type II superlattice infrared detector, which comprises, from bottom to top: a GaSb substrate, a GaSb buffer layer, a lower contact layer, an electron barrier layer, an absorption layer, a hole barrier layer, an upper contact layer, and a capping layer. The low dark current InAs / GaSb type II superlattice infrared detector also includes a passivation layer and electrodes.

[0022] In this invention, the thickness of the GaSb substrate is preferably 300~500μm, and more preferably 340~450μm.

[0023] In this invention, the parameters of the GaSb buffer layer include: a thickness preferably of 0.5~1μm, more preferably 0.6~0.9μm, and p-type doping with Be, with a doping concentration preferably of 1×10⁻⁶. 16 ~5×10 16 cm -3 A further preferred value is 1.5 × 10⁻⁶. 16 ~4×10 16 cm -3 .

[0024] In this invention, the lower contact layer is preferably an n-type InAs / GaSb type II superlattice lower contact layer; the parameters of the lower contact layer include: the superlattice period is preferably composed of 8ML InAs / 8ML GaSb, the total thickness is preferably 0.5~1μm, more preferably 0.7~0.9μm, and Si is used for n-type doping, with a doping concentration preferably 1×10⁻⁶. 18 ~3×10 18 cm -3 A further preferred value is 1.5 × 10⁻⁶. 18 ~2.5×10 18 cm -3 .

[0025] In this invention, the electronic barrier layer is preferably an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice electronic barrier layer; the parameters of the electronic barrier layer include: the superlattice period is preferably composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, more preferably 2.5~3ML InAs / 2.5~3ML GaSb / 1.5~2ML AlSb / 2.5~3ML GaSb, and the total thickness is preferably 100~300nm, more preferably 120~200nm.

[0026] In this invention, the absorption layer is preferably an unintentionally doped InAs / GaSb type II superlattice absorption layer; the absorption layer preferably includes a mid-wave infrared absorption layer and / or a long-wave infrared absorption layer, more preferably a mid-wave infrared absorption layer or a long-wave infrared absorption layer; the total thickness of the absorption layer is preferably 1.5~3μm, more preferably 1.8~2.5μm.

[0027] In this invention, the superlattice period of the mid-wave infrared absorption layer is preferably composed of 8~10ML InAs / 1ML InSb / 8~10ML GaSb, and more preferably 9~10ML InAs / 1ML InSb / 9~10ML GaSb.

[0028] In this invention, the superlattice period of the long-wave infrared absorption layer is preferably composed of 12~15ML InAs / 1ML InSb / 6~8ML GaSb, and more preferably 13~14ML ​​InAs / 1ML InSb / 7~8ML GaSb.

[0029] In this invention, the hole barrier layer is preferably an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice hole barrier layer; the parameters of the hole barrier layer include: the superlattice period is preferably composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, more preferably 3~4ML InAs / 3~4ML GaSb / 1.5~2ML AlSb / 3~4ML GaSb, and the total thickness is preferably 100~200nm, more preferably 100~150nm.

[0030] In this invention, the upper contact layer is preferably a p-type InAs / GaSb type II superlattice upper contact layer; the parameters of the upper contact layer include: the superlattice period is preferably composed of 8ML InAs / 8ML GaSb, the total thickness is preferably 0.3~0.8μm, more preferably 0.4~0.7μm, and p-type doping is performed using Be, with a doping concentration preferably 1×10⁻⁶. 18~3×10 18 cm -3 A further preferred value is 1.5 × 10⁻⁶. 18 ~2.5×10 18 cm -3 .

[0031] In this invention, the capping layer is preferably an unintentionally doped InAs layer with a thickness of 5-20 nm, more preferably 8-15 nm.

[0032] In this invention, the passivation layer is preferably an Al2O3 layer with a thickness of 50-200 nm, more preferably 70-180 nm.

[0033] In this invention, the electrode preferably includes an upper electrode and a lower electrode, with the upper electrode disposed on the capping layer and the lower electrode disposed on the lower contact layer; the electrode is preferably a Ti / Pt / Au metal layer with a thickness of preferably 20~50nm / 20~50nm / 100~200nm, and more preferably 30~50nm / 30~50nm / 100~150nm.

[0034] This invention also provides a method for fabricating a low dark current InAs / GaSb type II superlattice infrared detector, comprising the following steps: (1) Select a GaSb single crystal substrate with (001) crystal orientation and clean it with acetone, ethanol and deionized water in sequence to remove surface contaminants and oxide layer; (2) A GaSb buffer layer was grown on a GaSb substrate using molecular beam epitaxy (MBE) technology. The growth temperature was 500~550℃ and the growth rate was 0.5~1μm / h. A Be doping source was used for p-type doping. (3) An n-type InAs / GaSb type II superlattice lower contact layer is grown on the GaSb buffer layer; the growth temperature is 480~520℃, and n-type doping is performed using a Si doping source; (4) Grow an InAs / GaSb / AlSb / GaSb superlattice electronic barrier layer on the lower contact layer; the growth temperature is 520~540℃; (5) An InAs / GaSb type II superlattice absorption layer is grown on the electron barrier layer; In each superlattice period, an InSb interface layer is inserted between the InAs layer and the GaSb layer; The InSb interface layer is grown using migration-enhanced epitaxy (MEE): 1 mL of InSb is deposited at the GaSb-on-InAs interface; Specifically, after the InAs layer growth is completed, the As shutter is closed and the Sb shutter is opened to deposit In and Sb to form the InSb interface layer; After the GaSb layer growth is completed, the Sb shutter is closed and the As shutter is opened for As-soaking treatment, and the InAs layer of the next period is grown; The surface reconstruction and growth rate are monitored in real time by reflection high-energy electron diffraction (RHEED) throughout the superlattice growth process; (6) Grow an InAs / GaSb / AlSb / GaSb superlattice hole barrier layer on the absorption layer; the growth temperature is 520~540℃; (7) A p-type InAs / GaSb type II superlattice contact layer is grown on the hole barrier layer; the growth temperature is 500~520℃, and p-type doping is performed using a Be doping source; (8) Grow an InAs capping layer on the upper contact layer; (9) The unit mesa mask pattern is transferred to the capping layer by ultraviolet lithography, and then etched in the etching solution (a mixture of 98% citric acid aqueous solution, 90% phosphoric acid and 35% hydrogen peroxide in a volume ratio of 3:1:1) at 25°C for 5 min, until the lower contact layer is etched to form the mesa structure. (10) An Al2O3 passivation layer was deposited on the mesa sidewall using atomic layer deposition (ALD) technology; (11) An upper electrode is fabricated on the InAs capping layer and a lower electrode is fabricated on the lower contact layer mesa by using ultraviolet lithography, electron beam evaporation and lift-off processes.

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] The substrate is a (001) GaSb single crystal substrate with a thickness of 400 μm.

[0038] The GaSb buffer layer is 0.8 μm thick and is p-type doped with Be at a concentration of 2 × 10⁻⁶. 16 cm -3 .

[0039] The lower contact layer is an 8ML InAs / 8ML GaSb superlattice periodic layer with a total thickness of 0.9 μm. It is n-type doped with Si at a doping concentration of 2 × 10⁻⁶. 18 cm -3 .

[0040] The electronic barrier layer consists of a 3ML InAs / 3ML GaSb / 1.5ML AlSb / 3ML GaSb superlattice period with a total thickness of 150nm and is not intentionally doped.

[0041] The absorber layer consists of a 9 mL InAs / 9 mL GaSb superlattice period, with a total thickness of 2.2 μm, and is not intentionally doped. A 1 mL InSb interface layer is inserted between the InAs and GaSb layers in each period.

[0042] The hole barrier layer consists of a 3ML InAs / 3ML GaSb / 1.5ML AlSb / 3ML GaSb superlattice period with a total thickness of 100nm and is not intentionally doped.

[0043] The upper contact layer is an 8ML InAs / 8ML GaSb superlattice periodic layer with a total thickness of 0.6 μm. It is p-type doped with Be at a concentration of 2 × 10⁻⁶. 18 cm -3 .

[0044] The capping layer is an InAs layer with a thickness of 10nm, which is not intentionally doped.

[0045] The passivation layer is an Al2O3 layer with a thickness of 100 nm.

[0046] The upper electrode is disposed on the capping layer and is a Ti / Pt / Au metal layer with a thickness of 30nm / 30nm / 100nm; the lower electrode is disposed on the lower contact layer and is a Ti / Pt / Au metal layer with a thickness of 30nm / 30nm / 100nm.

[0047] Tests showed that the dark current density of the detector at 77K and a -0.5V bias voltage was 4.2 × 10⁻⁶. -7 A / cm 2 The peak detectivity reached 3.5×10⁻⁶. 12 cm·Hz 1 / 2 W -1 .

[0048] Example 2

[0049] The substrate is a (001) GaSb single crystal substrate with a thickness of 400 μm.

[0050] The GaSb buffer layer is 1 μm thick and is p-type doped with Be at a concentration of 3 × 10⁻⁶. 16cm -3 .

[0051] The lower contact layer is an 8ML InAs / 8ML GaSb superlattice periodic layer with a total thickness of 0.7 μm. It is n-type doped with Si at a doping concentration of 2.5 × 10⁻⁶. 18 cm -3 .

[0052] The electronic barrier layer consists of a 2.5ML InAs / 2.5ML GaSb / 2ML AlSb / 2.5ML GaSb superlattice period with a total thickness of 190nm and is not intentionally doped.

[0053] The absorber layer consists of a 14 mL InAs / 7 mL GaSb superlattice period, with a total thickness of 2.8 μm, and is not intentionally doped. A 1 mL InSb interface layer is inserted between the InAs and GaSb layers in each period.

[0054] The hole barrier layer consists of a 2.5ML InAs / 2.5ML GaSb / 2ML AlSb / 2.5ML GaSb superlattice period with a total thickness of 150nm and is not intentionally doped.

[0055] The upper contact layer is an 8ML InAs / 8ML GaSb superlattice periodic layer with a total thickness of 0.5 μm. It is p-type doped with Be at a concentration of 2.5 × 10⁻⁶. 18 cm -3 .

[0056] The capping layer is an InAs layer with a thickness of 15nm, which is not intentionally doped.

[0057] The passivation layer is an Al2O3 layer with a thickness of 150nm.

[0058] The upper electrode is disposed on the capping layer and is a Ti / Pt / Au metal layer with a thickness of 50nm / 50nm / 200nm; the lower electrode is disposed on the lower contact layer and is a Ti / Pt / Au metal layer with a thickness of 50nm / 50nm / 200nm.

[0059] Tests showed that the dark current density of the detector at 77K and a bias voltage of -0.5V was 8.6 × 10⁻⁶. -6 A / cm 2 The peak detectivity reached 6.6×10 10 cm·Hz 1 / 2 W -1 .

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low dark current InAs / GaSb type II superlattice infrared detector, characterized in that, From bottom to top, it includes: GaSb substrate, GaSb buffer layer, lower contact layer, electron barrier layer, absorption layer, hole barrier layer, upper contact layer, and capping layer. The low dark current InAs / GaSb type II superlattice infrared detector also includes a passivation layer and electrodes; The lower contact layer is an n-type InAs / GaSb type II superlattice lower contact layer; the electron barrier layer is an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice electron barrier layer; the absorption layer is an unintentionally doped InAs / GaSb type II superlattice absorption layer; the hole barrier layer is an unintentionally doped InAs / GaSb / AlSb / GaSb superlattice hole barrier layer; and the upper contact layer is a p-type InAs / GaSb type II superlattice upper contact layer.

2. The low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The absorption layer includes a mid-wave infrared absorption layer and / or a long-wave infrared absorption layer; the total thickness of the absorption layer is 1.5~3μm.

3. The low dark current InAs / GaSb type II superlattice infrared detector according to claim 2, characterized in that, The superlattice period of the mid-wave infrared absorption layer is composed of 8~10ML InAs / 1ML InSb / 8~10ML GaSb.

4. The low dark current InAs / GaSb type II superlattice infrared detector according to claim 2, characterized in that, The superlattice period of the long-wave infrared absorption layer is composed of 12~15ML InAs / 1ML InSb / 6~8ML GaSb.

5. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The parameters of the GaSb buffer layer include: a thickness of 0.5~1.0 μm, p-type doping with Be, and a doping concentration of 1×10⁻⁶. 16 ~5×10 16 cm -3 .

6. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The parameters of the lower contact layer include: the superlattice period consists of 8 mL InAs / 8 mL GaSb, the total thickness is 0.5~1 μm, and it is n-type doped with Si at a doping concentration of 1×10⁻⁶. 18 ~3×10 18 cm -3 .

7. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The parameters of the upper contact layer include: the superlattice period consists of 8 mL InAs / 8 mL GaSb, the total thickness is 0.3~0.8 μm, and it is p-type doped with Be at a doping concentration of 1×10⁻⁶. 18 ~3×10 18 cm -3 .

8. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The parameters of the electronic barrier layer include: the superlattice period is composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, and the total thickness is 100~300nm.

9. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The parameters of the hole barrier layer include: the superlattice period is composed of 2~4ML InAs / 2~4ML GaSb / 1~2ML AlSb / 2~4ML GaSb, and the total thickness is 100~200nm.

10. A low dark current InAs / GaSb type II superlattice infrared detector according to claim 1, characterized in that, The capping layer is an unintentionally doped InAs layer with a thickness of 5-20 nm; the passivation layer is an Al2O3 layer with a thickness of 50-200 nm; the electrode includes an upper electrode and a lower electrode, with the upper electrode disposed on the capping layer and the lower electrode disposed on the lower contact layer; the electrode is a Ti / Pt / Au metal layer.

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