Vapor Levitation Epitaxy—A New Concept in Crystal Growth

Abstract

Bell Communications Research (Bellcore) scientists Herbert M. Cox, Steve G. Hummel and Vassilis G. Keramidas recently unveiled a revolutionary crystal growth process used in growing semiconductor materials of importance to many areas of fiber optic communications. The technique, called Vapor Levitation Epitaxy (VLE), is based on the concept of floating wafers while growing thin film crystalline layers on them. The method has produced exceptionally pure materials such as GaAs, InP, InGaAs, InGaAsP and GalnP. The capability of growing ultra high purity materials combined with the ability to grow ultra thin layers-a few atoms thick-makes the new technique uniquely powerful. In addition, exceptional uniformity of thickness and materials composition can be achieved across the whole area of two-inch diameter wafers. These capabilities are essential to the growth of multilayer structures needed for new applications in photonic and electronic devices and integrated circuits, and integrated opto-electronics for fiber optic communications. The VLE apparatus has two adjacent growth chambers capped with porous disks and a horizontal levitation track with a series of small gas jet holes along its center (see Figure 1). The gas jets suspend the wafer on a cushion of gas as it is moved between the wafer loading area and the growth region of the apparatus. Each growth chamber is supplied independently with vapors for the particular material to be grown. During growth, the wafer floats a few tenths of a millimeter above the chamber suspended stably by the growth vapors as