MOCVD-grown compressively strained C-doped InxGa1−xAs1−ySby with high-In/Sb content for very low turn-on-voltage InP-based DHBTs

We investigated metalorganic chemical vapor deposition of C-doped high-In-and-Sb-content compressively strained InxGa1−xAs1−ySby and examined InP-based heterojunction bipolar transistors (HBTs) with low base-emitter turn-on voltage. By lowering the growth temperature to 530 °C, the etching effect of CBr4 is suppressed, which is consistent with the results of thermodynamic calculations. We obtained high hole concentration of mid-1019 cm−3 with the In content of over 0.20. The base-emitter voltage (VBE) at collector current density (JC) of 10 nA/μm2 of large-area HBTs with the high-In-and-Sb-content compressively strained InxGa1−xAs1−ySby base is lower than those of the HBTs with a tensile strained InxGa1−xAs1−ySby or GaAs1−ySby base, owing to the reduction of the band gap of the base layer. We fabricated InP/In0.20Ga0.80As0.55Sb0.45/InP HBTs with a 0.25-μm-wide emitter and obtained the VBE of 0.66 V at JC of 1 mA/μm2. At JC=13 mA/μm2, the device exhibits peak current-gain cut-off frequency of over 400 GHz, which is comparable to the value for GaAs1−ySby-base HBTs with the same base and collector thicknesses.