Surface passivation of GaInAsSb photodiodes with thioacetamide

Abstract

AlGaAsSb/GaInAsSb heterojunction mesa photodiodes having 2.2 µm cutoff wavelength, grown by MBE on (p) GaSb substrates, have been passivated using thioacetamide CH 4 CSNH 2 and ammonium sulphide (NH 4 ) 2 S. Superior characteristics were obtained from devices processed with thioacetamide in acid medium (pH = 2.4). At room temperature the surface leakage currents were suppressed, and the photodiodes showed R 0 A product as high as 16 Ωcm 2 and detectivity D* (2 µm, 0 V) ~ 10 10 cm Hz 1/2 W -1. A model explaining sulfuration mechanisms with thioacetamide and (NH 4 ) 2 S is proposed.

Passivation of GaSb and InAs by pH-activated thioacetamide

“…detail [6,7,21,22,24,25]. Surface passivation by TAM compares favorably to that by inorganic sulfides [25] and offers advantages such as milder reaction conditions and the ability to passivate under both acidic and basic conditions.…”

“…Most published accounts focus on the effects of passivation on device performance without attempting to directly characterize the chemistry of the passivated surface [1][2][3][4][5][6][7]. As a result, surprisingly little is known about the chemical effects of various passivation treatments, despite the widespread research on the effects of passivation on performance of III-V devices.…”

“…Sulfur passivation has been used effectively to passivate exposed surfaces of III-V semiconductor devices [15][16][17][18][19][20][21][22][23][24][25], and has been previously attempted for T2SLs [2][3][4]7]. Historically, most common sulfur passivation treatments have been performed in aqueous solutions of inorganic sulfides, such as (NH 4 ) 2 S x [16,17,23,[26][27][28] or Na 2 S [18,26,27,29].…”

“…In devices, III-V materials typically are not used separately and independently, but rather as alternating layers in superlattices. For example, Type-II superlattices (T2SLs) of InAs and GaSb are emerging as a promising material system for mid-and long-wavelength IR LEDs [8] and photodetectors [1][2][3][4][5]7,[9][10][11][12][13][14]. In these IR detectors, doped T2SLs are etched through the junction to produce an array of mesa-isolated photodiodes [3,4]; i.e., both superlattice materials are exposed to the ambient surroundings in these devices.…”

Mid-infrared GaSb-based resonant tunneling diode photodetectors for gas sensing applications

“…21 In addition, oxidation of Ga(InAs)Sb gives rise to leakage currents through the formation of a semi-metallic conductive layer of Sb at the surface. 29 Therefore, a Si3N4/SiO2 passivation is applied for sidewall leakage…”