High reliability InGaP/GaAs HBT

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Abstract
Excellent long term reliability InGaP/GaAs heterojunction bipolar transistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T=10000 h) in a sample lot of ten devices (L=6.4 /spl mu/m /spl times/20 /spl mu/m) under moderate current densities and high-temperature testing (J/sub c/=25 kA/cm/sup 2/, V/sub ce/=2.0 V, Junction Temp =264/spl deg/C). The dc current gain for large area devices (L=75 /spl mu/m /spl times/75 /spl mu/m) at 1 kA/cm/sup 2/ at a base sheet resistance of 240 ohms/sq (4/spl times/10/sup 19/ cm/sup -3/@700 /spl Aring/) was over 100. The dc current gain before reliability testing (L=6.4 /spl mu/m /spl times/10 /spl mu/m) at 0.8 kA/cm/sup 2/ was 62. The dc current gain (0.8 kA/cm/sup 2/) decreased to 57 after 10000 h of reliability testing. The devices showed an f/sub T/=61 GHz and f/sub max/=103 GHz. The reliability results are the highest ever achieved for InGaP/GaAs HBT and these results indicate the great potential of InGaP/GaAs HBT for numerous low- and high-frequency microwave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which result from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs.

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