High DC current gain InGaP/GaAs HBTs grown by LP-MOCVD

Abstract

The high current gain of InGaP/GaAs heterojunction bipolar transistors (HBTs) grown under optimised growth conditions using MOCVD is demonstrated. Large area (60 µm × 60 µm) samples of InGaP/GaAs HBTs are grown and fabricated for DC characterisation. These devices show Gummel plots with nearly ideal I-V characteristics (nc = 1.00 and nb = 1.09). Measured current gain of the devices with a base sheet resistance Rb of 236 Ω/sq is 130 at a collector current Ic of 1 mA and 147 at the collector current density of 1 kA/cm2 (Ic = 39.1 mA). The current gain to base sheet resistance ratio is 0.623 at 1 kA/cm2, which is the highest value ever reported. The optimised growth condition improves the current gain in the entire range of the collector current. The current gain is as high as 92 at an Ic of 10 µA. These results are the best that have ever been demonstrated with InGaP/GaAs HBTs. The data show that the MOCVD growth condition is an important factor in achieving high current gain in InGaP/GaAs HBTs.