Abstract

A compositionally graded InGaAlAs:C base layer is inserted in an InP-based HBT grown by LP-MOVPE with a novel non-gaseous source configuration. Due to the addition of 6% Al the active hole concentration in the HBT base layer, deduced from Hall measurements, is increased from 1.5 10 19 to 3.8 10 19 cm -3 . Moreover, an In-grading within the base layer results in an intrinsic electric field of about 5.4 kV/cm. A high dc current gain of β = 35 is provided at a high p-type doping level. First HBT devices exhibit a current gain cut-off frequency of fT = 117 GHz and an unilateral gain cut-off frequency of 90 GHz (not de-embedded).