Abstract: An improved HBT of the invention reduces the current blocking effect at the base-collector interface. Nitrogen is incorporated at the base-collector interface in an amount sufficient to reduce the conduction band energy of the collector at the base-collector interface to equal the conduction band energy of the base. In a preferred embodiment, a nitrogen concentration on the order of 2% is used in a thin ˜20 nm layer at the base-collector interface. Preferred embodiment HBTs of the invention include both GaAs HBTs and InP transistors in various layer structures, e.g., single and double heterojunction bipolar transistors and blocked hole bipolar transistors.