Graded band gap for dark-current suppression in long-wave infrared W-structured type-II superlattice photodiodes

Abstract

A new W-structured type-II superlattice photodiode design, with graded band gap in the depletion region, is shown to strongly suppress dark currents due to tunneling and generation-recombination processes. The long-wave infrared (LWIR) devices display 19%–29% quantum efficiency and substantially reduced dark currents. The median dynamic impedance-area product of 216Ωcm2 for 33 devices with 10.5μm cutoff at 78K is comparable to that for state-of-the-art HgCdTe-based photodiodes. The sidewall resistivity of ≈70kΩcm for untreated mesas is also considerably higher than previous reports for passivated or unpassivated type-II LWIR photodiodes, apparently indicating self-passivation by the graded band gap.

Design and Development of Two-Dimensional Strained Layer Superlattice (SLS) Detector Arrays for IR Applications

“…In addition, type II SLS detectors based on the 6.1 Å family of materials can be passively cooled, thus reducing the cryocooler burden, and these take advantage of the relatively large installed III-V material manufacturing base [18]. These properties have enabled the fabrication of large format IR FPAs based on type II SLS suitable for high-resolution thermal imaging applications including space-borne surveillance systems, low-background night vision, and missile detection [19][20][21][22][23][24][25][26].…”

“…These include gradedgap W- [19], M- [20], and N-structures [32]; buried junction nBn [21], pBp [22], and pBn [33] designs; and complementary barrier infrared detector (CBIRD) [23] and pBiBn [24] architectures. These device implementations are the result of exploitation of the material, electrical, and optical properties in type II SL materials for optimization of detector performance, which can benefit and advance a diverse array of applications.…”

Carrier Lifetime Measurements in Long-Wave Infrared InAs/GaSb Superlattices Under Low Excitation Conditions

“…[1][2][3] In the past several years, major efforts have been made to improve the performance of T2-SLS photodetectors regarding growth, processing, and structural design. [4][5][6][7] Current designs utilize a p À -doped absorber and heterojunction barriers to reduce the generation-recombination and tunneling components of dark current. 6 The performance of such photodetectors was reported to be limited by the Shockley-Read-Hall (SRH) carrier recombination process in the absorber.…”

“…[4][5][6][7] Current designs utilize a p À -doped absorber and heterojunction barriers to reduce the generation-recombination and tunneling components of dark current. 6 The performance of such photodetectors was reported to be limited by the Shockley-Read-Hall (SRH) carrier recombination process in the absorber. 8 We previously reported the measurement of minority carrier lifetime in a LWIR T2-SLS structure with energy gap of 0.12 eV at 77 K. 9 The SRHlimited lifetime of 30 ns at 77 K was determined from the dependence of lifetime on excitation power using the OMR technique.…”

Defect states in type-II strained-layer superlattices

“…[13][14][15] It has been suggested, 6 on the basis of recent atomic-scale theory and measurements of InAs defect levels, 16 that shallow acceptors and deep levels would behave differently in superlattice structures from bulk InAs. The calculations in Fig.…”