Graded base type-II InP/GaAsSb DHBT with f/sub T/=475 GHz

Abstract

The first demonstration of a Type-II InP/GaAsSb double heterojunction bipolar transistor (DHBT) with a compositionally graded InGaAsSb to GaAsSb base layer is presented. A device with a 0.4 6 m 2 emitter dimensions achieves peak of 475 GHz ( MAX = 265 GHz) with current density at peak exceeding 12 mA/ m 2 . The structure consists of a 25-nm InGaAsSb/GaAsSb graded base layer and 65-nm InP collector grown by MBE with breakdown voltage 4 V which demonstrates the vertical scaling versus breakdown advantage over type-I DHBTs.

Improvement of GaAsSb alloys on InP grown by molecular beam epitaxy with substrate tilting

“…1-3 In contrast to the conventional InAlAs/InGaAs and InGaAs/GaAsSb heterojunctions with a much larger conduction band offset, 4-6 the smaller conduction band offset of GaAsSb/InP is more favorable for the high-speed operations, such as those of double heterojunction bipolar transistors (DHBT). [7][8][9] However, the GaAs x Sb 1Àx (x $ 0.5) alloys exhibit a miscibility gap, which poses a challenge for crystal growth. Presently, only nonequilibrium techniques such as metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) have successfully grown GaAs x Sb 1Àx layers over the entire range of x values.…”

Low Turn-On Voltage and High-Current $\hbox{InP}/ \hbox{In}_{0.37}\hbox{Ga}_{0.63}\hbox{As}_{0.89}\hbox{Sb}_{0.11}/\hbox{In}_{0.53}\hbox{Ga}_{0.47}\hbox{As}$ Double Heterojunction Bipolar Transistors

“…Moreover, the low electron diffusivity in GaAsSb also adversely affects the current gain and the high-frequency performance [3]. To solve these issues, a GaAsSb/InGaAsSb graded base layer has been proposed to reduce the base transit, which results in an f T of 475 GHz [4]. The combination of an InAlP emitter and an AlGaAsSb graded base has shown to be effective in increasing the current gain [5].…”

High-speed InGaAsSb/InP double heterojunction bipolar transistor with composition graded base and InAs emitter contact layers

“…Recently, type-II GaAsSb/InP DHBT has been advanced to achieve RF performance similar to type-I InGaAs/InP DHBTs [1][2][3]. The compositional graded GaAsSb-InGaAsSb base enhances the electron transit through the base region and, therefore, improves the high-peed characteristics of the DHBT.…”