HIGH-RELIABILITY INGAP GAAS HBT

Excellent long term reliability InGaP/GaAs heterojunction bipolar tran sistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T = 10000 h) in a sam ple lot of ten devices (L = 6.4 mu m x 20 mu m) under moderate current densities and high-temperature testing (J(c) = 25 kA/cm(2), V-ce = 2. 0 V, Junction Temp = 261 degrees C). The de current gain for large are a devices (L = 75 mu m x 75 mu m) at 1 kA/cm(2) at a base sheet resist ance of 240 ohms/sq (4 x 10(19) cm(-3) @ 700 Angstrom) was over 100. T he de current gain before reliability testing (L = 6.4 mu m x 10 mu m) at 0.8 kA/cm(2) was 62. The de current gain (0.8 kA/cm(2)) decreased to 57 after 10000 h of reliability testing. The devices showed an f(T) = 61 GHz and f(max) = 103 GHz. The reliability results are the highes t ever achieved for InGaF/GaAs HBT and these results indicate the grea t potential of InGaP/GaAs HBT for numerous low- and high-frequency mic rowave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which re sult from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs.