An efficient heat-spreader design: First demonstration on InGaP/graded InGaAs base/GaAs collector-up HBTs

摘要

An efficient heat-spreader design, demonstrated on n-p-n InGaP/graded InGaAs base/GaAs collector-up heterojunction bipolar transistors (HBTs) for the first time, is proposed to achieve high speed and thermal dissipation performances. The collector-up HBT, with a graded InGaAs base, has been successfully fabricated using a three-stage selective-area-regrowth technique. A unity-gain cutoff frequency fr = 55 GHz and a maximum frequency of oscillation f_(max)= 74 GHz were obtained from prototype devices with a large collector area of 3.5×40 μm~2. Moreover, through proper thinning process, the maximum junction temperature and thermal coupling within the transistors were effectively decreased. It is shown that the thermal management for power amplifiers, based on the developed HBT, used in next-generation cellular phones can be enhanced.