MOMBE and MOVPE—A comparison of growth techniques

Abstract

Since its inception in 1968 /l/ MOVPE (metal organic vapor phase epitaxy) or NOCVD (metal organic chemical vapor deposition) has undergone a steady development. Operation at reduced pressures /2/ enables better homogeneity of deposited layers /3/ and sophisticated gas manifolds allow fast switching and abrupt changes of composition in the deporited films /J/. Especially for III-V semiconductor layers and layered structures HOVPE now has become a widespread growth technique for a range of electronic and optoelectronic devise structures like RENTS /5/, lasers /6/, photodetectors /7/ or complete integrated circuits /8/. Although it is being successfully used for production of layers, the MOVPE process is only partly understood since the interplay of gas phase and surface reactions makes an investigatian of this growth system difficult. To shed more light on the surface reactions in IIOVPE, in our laboratory a study was started to investigate these processes under uhv conditions /9/. This approach, which we called metalorganic molecular beam epitaxy (HOIIBE) has developed into a powerful growth technique in its own right. It was subsequently named chemical beam epitaxy (CBE) by others using a slightly modified version /lo/. Although originally very closely related to MOVPE it is widely considered as a special form of HBE. The purpose of this paper is to compare deposition eauipment, growth kinetics and the aualitv of thedeposited layers and to di;cuss the siniliatd for Gab which still is the besi investigated III-V material. Although MOHEJE is a relatively new technique its rapid development raises high expectations for the quality of the material that can be obtained by this approach in the near future. It will be argued in this paper, that it has the potential to become a fabrication process for applications where a high level of control is required.