High-speed performance of InP/In0.53Ga0.47As/InP double-heterojunction bipolar transistors

Abstract

A theoretical comparison of In_0.53Ga_0.47As/InP and Al_0.3Ga_0.7As/GaAs heterojunction bipolar transistors has been undertaken in an effort to determine the relative merits of these material systems. The analysis uses a compact transistor model and considers devices with self‐aligned geometries including both extrinsic and intrinsic parameters. The high electron mobility in the In_0.53Ga_0.47As base layer and high peak velocity of electrons in the collector depletion layer result in a current gain cutoff frequency in excess of 150 GHz for an InP/In_0.53Ga_0.47As transistor with base thickness of 0.1 μm. Calculations revealed, however, that maximum oscillation frequency is strongly dependent on the contact resistance of the p‐type base layer, even for a self‐aligned base transistor. A maximum oscillation frequency of 138 GHz is theoretically predicted for an InP/In_0.53Ga_0.47As transistor with base thickness of 0.06 μm, base doping of 1×10²⁰ cm⁻³, a p‐type contact resistance of 1.0×10⁻⁷ Ω cm², a current density of 5×10⁴ A/cm², and a V_CB of 5 V.