Chakrapani Gajanan Jambotkar

Heterojunction bipolar transistors

The concept of the heterojunction bipolar transistor (HBT) was introduced by William Shockley in 1948 (U.S. patent: 2569347). The detailed theory of the device was developed by Kromer in 1957 (Kromer, 1957). The great potential advantages of such a heterostructure design over the conventional homostructure design have long been recognized (Kromer, 1957, 1982), but it was not until the early 1970s, that technology evolved to build practically useful transistors of this kind. The situation began to change with the emergence of liquid-phase epitaxy (LPE) as a technology for III—V compound semiconductor heterostructures. Since the mid-1970s, two additional very promising technologies have appeared: metal—organic chemical vapor deposition (MOCVD) (Dupuis et al., 1979) and molecular beam epitaxy (MBE) (Cho and Arthur, 1975). Impressive results on MOCVD and MBE-grown heterojunction bipolar transistors have been attained (Konnzai et al., 1979; Beneking and Su, 1980).