Metalorganic chemical vapor deposition

Sophisticated technologies1–19 for the growth of high-quality epitaxial layers of compound semiconductor heterostructure materials on single crystal semiconductor substrates are becoming increasingly important to the development of the semiconductor electronics industry. Historically, germanium was used in the invention of the point contact transistor and was the first material used in commercial applications. The drawback of germanium, however, is that it does not have a stable native oxide to eliminate surface effects. Silicon, with its extraordinary native oxide providing electronic and planar processing opportunities unavailable in other material systems, eventually replaced germanium and now dominates the semiconductor industry. As high speed electronic devices approach the fundamental limits of silicon and as optical and optoelectronic semiconductor devices become important. the HI-V compound semiconductors have become the state-of-the-art material. The advantages of the 111-V compounds are many. Unlike silicon, which is an indirect energy gap semiconductor. many compound semiconductors are direct energy gap semiconductors. This promotes efficient light emission and absorption. Low-field electron mobilities are generally higher than for silicon. The principal disadvantage of the Ill-V materials is the lack of a native oxide having the useful properties of SO2. This is more than offset by the novel device structures possible with the heterostructure, which is a layered structure of different materials having different energy gaps but having nearly the same lattice constant. High electron mobility transistors11,20 and quantum well heterostructure laser diodes 21.23 are just a few of the high performance devices which have been developed with heterostructures and compound semiconductors. To create abrupt, perfect heterojunctions, the deposition of high quality epitaxial layers is essential.