III-Nitride semiconductor growth by MBE:: Recent issues

Semiconductor III-Nitrides, such as GaN, AlN, InN and their ternaries, have recently gained considerable attention after an uneven effort around the first half of the 1970s which paved the way to intense activity in the preceding decade. This is in part due to early obstacles achieving high quality layers, particularly those with p-type conductivity. With marketing of blue LEDs, the interest and consequently the effort grew to the point that CW lasers, high power amplifiers, and UV detectors have been added to the list of devices made in this material system. GaN and its allied semiconductors are grown with a variety of techniques. Generally, thick GaN layers are grown with hydride vapor phase epitaxy whereas the thin ones and heterojunctions formed by the above mentioned binaries and their ternaries are grown by organometallic vapor phase epitaxy and molecular beam epitaxy. OMVPE uses ammonia and metalorganics for group V and III elements whereas MBE uses either ammonia or RF activated N-2, and metal for group III elements. Among the above mentioned thin-film growth methods, only the issues pertaining to MBE will be reviewed in this paper. (C) 2001 Kluwer Academic Publishers.