High-Gain Low Turn-On Voltage AlGaAs/GaAsNSb/GaAs Heterojunction Bipolar Transistors Grown by Molecular Beam Epitaxy

Abstract

AlGaAs/GaAsNSb heterojunction bipolar transistors (HBTs) with low turn-on voltage have been fabricated. The turn-on voltage of the device fabricated from an as-grown sample is ∼180 mV lower than that of a conventional AlGaAs/GaAs HBT. The effect of rapid thermal annealing on device performance is an increase in the gain from ∼8.5 to ∼20. However, the knee voltage of the annealed sample (∼3 V), as well as the turn-on voltage, is also higher compared with that of the as-grown sample (∼1.5 V).

Recent Progress in Dilute Nitride-antimonide Materials for Photonic and Electronic Applications

“…The collector and base current ideality factors were 1.01 and 1.1, respectively. However, this device showed a DC gain of only ~4, which is low compared to that reported 56 for an HBT with GaN 0.005 As 0.915 Sb 0.08 (N~0.5%) base layer (DC gain ~8.5), and a device with nitrogenfree low band gap base layer 57 such as GaAs 0.92 Sb 0.8 (DC gain ~20). Consistent with what has been reported for InGaAsN HBTs, 58 the DC gain degrades as the N concentration is increased.…”

“…However, due to the low N concentration (N~0.5%, E g ~1.2eV) used in the GaN 0.005 As 0.915 Sb 0.08 HBT base layer reported in ref. [ 56 ], there is significant room for improving the reduction in the turn-on voltage beyond the reported 80mV if higher N concentration coupled with optimized RTA conditions are used. In this section, we describe the use of GaN 0.03 As 0.89 Sb 0.08 (N~3%, E g~0 .9eV) as the base layer of AlGaAs/GaNAsSb HBT fabricated on GaAs substrate.…”

“…Recently, the use of GaNAsSb as the base layer in a GaAs substrate HBT has been reported. 54,55 Subsequently, Lew et al 56 reported the first AlGaAs/GaNAsSb HBT on a GaAs substrate with current gain of ~20, and established the benefit of rapid thermal annealing (RTA), albeit based on non-optimized condition, for improving the AlGaAs/GaAsNSb HBT performance. However, due to the low N concentration (N~0.5%, E g ~1.2eV) used in the GaN 0.005 As 0.915 Sb 0.08 HBT base layer reported in ref.…”

“…Detail of fabrication can be found elsewhere. 12 The first sample is an as-grown sample and the second sample is previously subjected to rapid thermal annealing. Fig.…”

“…In this paper, we will review the recent progress in the GaNAsSb based photonic and electrical devices based on our previously published works in refs. [6][7][8][9][10][11][12]. The review will be categorized into four sections, namely photodetector, optical waveguide, photoconductive switch and heterojunction bipolar transistor.…”