Fabrication of 15-$\mu$ m Pitch $640\times512$ InAs/GaSb Type-II Superlattice Focal Plane Arrays

Abstract

We present the fabrication of large format 640 × 512, 15-µm pitch, mid-wave infrared region (MWIR) InAs/GaSb type-II superlattice (T2SL) focal plane array (FPA). In this report, the details of device design and fabrication processes are withheld adhering to the common practice of most of the manufactures and developers because of the strategic importance; however, information about fabrication processes of T2SLs FPA is presented to a certain extent. Comparison of etching techniques, passivation materials and methods, and substrate thinning (mechanical and chemical) is given besides of details regarding the standard ohmic contact and indium (In) bump formations. Morphological investigations of fabrication step are included. Large area pixels, 220 µm × 220 µm, fabricated by different etching methods and passivation materials/methods are compared in terms of dark current levels. Wet passivation with (NH 4) 2 S is discussed in terms of morphological investigations, and dark current results are compared with untreated samples. Large area pixel level characterizations as well as image level benchmarking of mechanical and chemical substrate thinning are reported. Effect of GaSb substrate on device performance and the way of reducing stress of In bumps are revealed. The importance of complete substrate removal is demonstrated through FPA images. Index Terms-Fabrication, focal plane array, infrared photodetectors, mid-wave infrared region, type-II superlattice. I. INTRODUCTION A N INFRARED device is fabricated by executing consecutive process steps that start with epilayer growth. Fabrication steps being well-established and feasible plays a decisive role in the performance of a device. Therefore, research groups and developers work constantly for reaching optimum fabrication processes in order to fabricate highly qualified sensors. For InAs/GaSb T2SLs, FPA fabrication is Manuscript

High Performance 15-μm Pitch 640 × 512 MWIR InAs/GaSb Type-II Superlattice Sensors

“…Yielded results of differently passivated samples were compared with unpassivated large area diode in Ref. [26]. According to previous study, polyimide passivation has shown relatively lower dark current than the other passivation methods investigated in detail.…”

Emerging Type‐II Superlattices of InAs/InAsSb and InAs/GaSb for Mid‐Wavelength Infrared Photodetectors

“…[ 21–23,190,240–243 ] For the FPA detectors, it is a crucial requirement to not only reduce the cooling power by enabling the noncryogenic operation but also to achieve good operability, uniformity, stability, reproducibility, and scalability via fabricating large format and small pitch FPAs. In recent years, developments of Ga‐based InAs/Ga(In)Sb and Ga‐free InAs/InAsSb T2SL have been carried out by several groups targeted at MWIR [ 57,226,244–247 ] and LWIR [ 247–249 ] FPAs. Figure a summarizes the quantum efficiency of current state‐of‐the‐art detector technologies including MCT, QWIP, nBn , and T2SL FPAs in the MWIR regime.…”

Residual stress distribution and flatness of dislocation-free Te-GaSb (100) substrate

“…Gallium antimony (GaSb), a binary Group III-V compound semiconductor, has become established as an important material in the manufacture of infrared opto-electronic devices and thermophotovoltaic cells. GaSb is a particularly effective substrate material for use in type-II InAs/GaSb superlattice infrared detectors in the medium and long wavelength, [1][2][3][4] which has enabled the rapid development of several detector technologies. When compared with more established mercury cadmium telluride material systems, the development of detector structures established on a complex strained layer superlattice deposited by molecular beam epitaxy offers a lower cost and more accessible technology.…”