We have fabricated and discussed the performances of the and HEBTs. From the calculation, an emitter thickness not smaller than 230 and 320 Å is needed to eliminate the emitter-base (E-B) potential spike for an and an HEBTs, respectively. For the studied HEBT, a wide emitter thickness of 700 Å degrades the d.c. performance due to the bulk recombination effect in the emitter neutral region under the large E-B forward bias. In addition, we observe a multiple S-shaped NDR resulting from an avalanche multiplication and successive barrier lowering process as operated in the inverted mode. Whereas the HEBT with an emitter thickness of 500 Å is properly designed to obtain a high current gain and a low offset voltage. However, we observe only a single S-shaped NDR for the HEBT. This is due to the barrier lowering effect attributed to the fact that the hole's and electron's accumulation occur simultaneously. Both the transistor action in normal operation mode and the presence of NDR make our studied devices very promising for the analog and logic circuit applications.