Self-aligned thin emitter C-doped base InP/InGaAs/InP DHBT's for high speed digital and microwave IC applications

Summary form only given. We have developed a new self-aligned thin emitter HBT process technology to fabricate high performance InP/InGaAs/InP DHBTs for digital and microwave IC applications. The epistructure which is grown by MOMBE features a C-doped base using a CBr/sub 4/ gas dopant source for stable device operation at high emitter current densities. The process technology uses combined ECR-RIE and wet etching and incorporates self-aligned emitter-base metallizations and spin-on-glass dielectric passivation. The 0.5 /spl mu/m InP collector structure results in much improved common emitter I-V characteristics (compared to InGaAs collectors) with low output conductance and high collector breakdown voltages (8-10 V). The insertion of thin n-doped 30 nm InGaAsP quaternary layers between the InP collector and InGaAs base allows high current density operation (J/sub c/=100 kA/cm/sup 2/) of the DHBT without current blocking. The use of a chirped InP/InGaAs superlattice emitter structure reduces the V/sub be/ of the devices with ideality factors very close to n=1.00. On-wafer s-parameter measurements demonstrated peak values (@J/sub c/=80 kA/cm/sup 2/, V/sub be/=2 V) of f/sub t/=100 GHz and f/sub max/=60 GHz for 2.4/spl times/9.4 /spl mu/m/sup 2/ transistors.