FABRICATION AND CHARACTERISTICS OF A GAINP GAAS HETEROJUNCTION BIPOLAR-TRANSISTOR USING A SELECTIVE BURIED SUB-COLLECTOR/

A C-doped GaInP/GaAs heterojunction bipolar transistor (BET) with a se lective buried sub-collector has been fabricated by two growth steps, The active HBT region was made on the selective buried sub-collector l ayer with minimum overlap of the extrinsic base and the sub-collector region resulting in substantial reduction of the base-collector capaci tance, The experiment shows that the base-collector capacitance is red uced to about half of that of a conventional HBT while the base resist ance remains unchanged resulting in a 40-50% increase in the maximum o scillation frequency, Both DC and RF characteristics are investigated and compared with a conventional HBT, A current gain of 40, cutoff fre quency of 50 GHz and maximum oscillation frequency of 140 GHZ were obt ained for the GaInP/GaAs HBT, It is demonstrated that the selective bu ried sub-collector provides an effective means for enhancing RF perfor mance of an HBT.