| Popis: |
Successful exploitation of the unique properties of III–V compound semiconductors has resulted in development of several new devices for optoelectronic and solid state microwave applications. These achievements, however, would not have been possible without major advances in the technology for epitaxial growth of such materials. Further improvements in device performances together with new applications of III–V compounds must be closely coupled with even more progress toward achievement of material with properties approaching the theoretical values. Chemical vapour deposition has emerged as the most common technique for epitaxial growth. Although significant improvements can be obtained through empirical methods of investigation of such processes, it is recognized that in the long run a firm fundamental understanding is essential. This realization provides the motivation for detailed, basic studies of the kinetics and thermodynamics of epitaxial growth by chemical vapour deposition. This review will examine the progress, both past and projected, in measurement and interpretation of the kinetics of vapour phase deposition of III–V epitaxial layers. The scope will be limited to near-atmospheric pressure, open flow epitaxial systems utilizing chemical transport. To date, most of the studies have concerned GaAs, GaP, InAs, InP, and their alloys. It has been demonstrated for GaAs, and for some of the other compounds as well, that, depending on the growth conditions, epitaxial deposition may proceed in two fundamentally different rate-limiting regimes. At low temperatures the rate is limited by a surface process; while at higher temperatures mass transport limitations appear to prevail. For mass-transport-limited deposition the sensitivity of the growth rate to various operating parameters can, in many cases, be predicted from theoretical considerations. Investigation of kinetically limited growth offers a path toward a fundamental understanding of the atomistic surface events that result in epitaxial growth. The progress in these areas will be discussed; in addition, experimental and theoretical tasks for future studies will be recommended. |
