Electrical and optical properties of infrared photodiodes using the InAs/Ga1−xInxSb superlattice in heterojunctions with GaSb

Abstract

The InAs/Ga1−xInxSb strained-layer superlattice (SLS) holds promise as an alternative III–V semiconductor system for long wavelength infrared detectors. In this article, we present the first investigation, to the best of our knowledge, of heterojunction photodiodes using this new material. The devices were grown by molecular beam epitaxy on GaSb substrates, and are comprised of a 38 Å InAs/16 Å Ga0.64In0.36Sb SLS used in double heterojunctions with GaSb contact layers. The structures were designed to optimize the quantum efficiency while minimizing transport barriers at the heterointerfaces. The photodiodes are assessed through the correlation of their performance with the SLS material quality and the detector design. X-ray diffraction, absorption, and Hall measurements are used to determine the SLS material properties. The electrical and optical properties of the photodiodes are determined using current–voltage and spectral responsivity measurements. At 78 K, these devices exhibit rectifying electrical behavior and photoresponse out to a wavelength of 10.6 μm corresponding to the SLS energy gap. The responsivity and resistance in these thin-layered (0.75 μm), unpassivated photodiodes result in a detectivity of 1×1010 cm √Hz/W at 8.8 μm and 78 K. Based upon the performance of these devices, we conclude that high-sensitivity operation of long-wavelength photovoltaic detectors at temperatures well in excess of conventional III–V band gap-engineered systems, and potentially in excess of HgCdTe, is feasible using this material system.

Structural properties of InAs/InAs1–xSbx type-II superlattices grown by molecular beam epitaxy

“…3 Extensive investigations of InAs/(In)GaSb type-II SLs have been carried out, including theoretical calculations of the band structure 4 and minority carrier lifetimes, 5 and significant success has been achieved for device performance in mid-, long-and very-long-wavelength infrared (VLWIR) ranges. [6][7][8][9] Strain-balanced InAs/InAs 1Àx Sb x SLs have been proposed as another possible alternative to HgCdTe, 10 and have already shown great promise for mid-IR laser and photodetector structures, 11 with photoluminescence emission in the range of 5-10 lm being achieved for SL structures containing Sb concentrations of 14À27%. 12 Recently, InAs/ InAs 1Àx Sb x SLs grown by metalorganic chemical vapor depostition (MOCVD) have been studied in more detail: these SLs showed excellent structural properties and strong optical response.…”

Long-wave infrared nBn photodetectors based on InAs/InAsSb type-II superlattices

“…[5][6][7] These advantages of T2SLs enable them to operate at higher temperatures, which is highly desirable for photodetector applications. 8,9 Although the feasibility of T2SLs for IR photodetectors has been studied for decades, the T2SL materials properties and device performance still have not reached the level predicted by theory. 6 One of the limiting factors of the most widely studied LWIR InAs/(In)GaSb T2SLs is the short minority carrier lifetime, which determines the dark current, detectivity, and ultimately the maximum operating temperature.…”

Quantum dots of InAs/GaSb type II superlattice for infrared sensing

“…In order to study the major components of the dark current at T = 80K, the current-voltage characteristic of the devices was modeled. Although the active layer of these devices consists of short period superlattices, bulk-based modeling of the dark current has been proven to give relatively accurate results [8,14,15]. We use an improved algorithm and more accurate calculations from Matlab based on formalism reported in Ref.…”