InP/GaAsSb Double Heterojunction Bipolar Transistor Emitter-Fin Technology With f _MAX = 1.2 THz

Abstract

We report a new InP/GaAsSb double heterojunction bipolar transistor (DHBT) emitter fin architecture with a record f MAX = 1.2 THz, a simultaneous f T = 475 GHz, and BV CEO = 5.4 V. The resulting BV CEO × f MAX = 6.48 THz-V is unparalleled in semiconductor technology. Devices were realized with a 20-nm-thick compositionally and impurity graded GaAsSb-base and a 125-nm InP collector. The performance arises because the process allows: 1) a tunable base-emitter access distance down to 10 nm; 2) the use of thicker base contact metals; and 3) the minimization of parasitic capacitances and resistances via precise lateral wet etching of the base-collector (B/C) mesa. Perhaps more significantly, InP/GaAsSb DHBTs with f MAX ≥ 1 THz are demonstrated with emitter lengths as long as 9.4 μm and areas as high as 1.645 μm 2 . Such an area is >6× larger than previously reported terahertz (THz) DHBTs, representing a breakthrough in THz transistor scalability. This attractive performance level is achieved with a very low dissipated power density which makes InP/GaAsSb DHBTs well-suited for high-efficiency millimeter-and submillimeter-wave applications. Furthermore, we provide the first large-signal characterization of a THz transistor with 94 GHz load-pull measurements showing a peak power-added-efficiency (PAE) of 32.5% (40% collector efficiency) and a maximum saturated power of 6.67 mW/μm 2 or 1.17 mW/μm of emitter length in a common-emitter configuration. Devices operate stably under large-signal conditions, with voltages nearly twice higher than those for peak small-signal performance.

Effect of emitter-base spacer design on the performance of InP/GaAsSb/InP DHBTs grown by MOCVD

“…InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) are very attractive in high-efficiency power amplifiers and terahertz devices [1][2][3][4]. Compared to the conventional type-I InP/InGaAs/InP DHBTs, type-II InP/GaAsSb/InP DHBTs can provide higher frequency and larger breakdown voltage at the same time, because the staggered band alignment between the GaAsSb base and InP collector contributes to both reducing the collector transit time and increasing the BV CEO [2][3][4][5]. Up to now, the best reported device performance is β = 42, f MAX = 1.2 THz, a simultaneous f T = 475 GHz, and BV CEO = 5.4 V using a 20 nm composition-graded base achieved by ETH-Zurich in 2022 [2].…”

“…Compared to the conventional type-I InP/InGaAs/InP DHBTs, type-II InP/GaAsSb/InP DHBTs can provide higher frequency and larger breakdown voltage at the same time, because the staggered band alignment between the GaAsSb base and InP collector contributes to both reducing the collector transit time and increasing the BV CEO [2][3][4][5]. Up to now, the best reported device performance is β = 42, f MAX = 1.2 THz, a simultaneous f T = 475 GHz, and BV CEO = 5.4 V using a 20 nm composition-graded base achieved by ETH-Zurich in 2022 [2]. However, the type-II alignment at the emitter-base (E-B) interface works as a barrier against electron flows, which increases the carrier recombination between the emitter conduction band and the base valance band as shown in figure 1, i.e.…”

High Power InP/Ga(In)AsSb DHBTs for Millimeter-Wave PAs: 14.5 dBm Output Power and 10.4 mw/μm2 Power Density at 94 GHz

“…III-V compound semiconductors such as GaAs, GaN, and InP offer high power handling capabilities as well as rising cut-off frequencies thanks to continued R&D activities. Among compound transistor technologies, "Type-II" double heterojunction bipolar transistors (DHBTs) based on the InP-Ga(In)AsSb material system provide the highest f T × BV CEO and f MAX × BV CEO products, as well as the highest f MAX in a bipolar transistor [1], [2]. Quaternary InP/GaInAsSb DHBTs also achieved the highest f T ever realized in a transistor [3].…”

“…Whereas InP/GaAsSb DHBTs have already demonstrated attractive power performances [2], [9], the large-signal properties of quaternary-based InP/GaInAsSb DHBTs have not previously been studied: the present work characterizes quaternary (0.3 × 9) μm 2 DHBTs in the common-emitter (CE) and common-base (CB) configurations, and contrasts them to those of conventional InP/GaAsSb DHBTs with a ternary base.…”

InP DHBT test structure optimization towards 110 GHz characterization

“…InP double heterojunction bipolar transistors (InP DHBT) have these characteristics. Both Type-I [1] and Type-II [2] DHBTs have already demonstrated fMAX above 1 THz while having breakdown voltages of 4.1 V and 5.4 V, respectively.…”