TABLE OF CONTENTS MBE is an incredibly fertile process. Its evolution into materials engineering and advanced device production is exceptional. Some current areas of research, relevant to the future viability of MBE, deserve mentioning.
Although intensity oscillations in RHEED patterns were recorded over six years ago by C. E. C. Wood, their nature was not well understood at that time and consequently their potential use was not perceived. The first published explanation is credited to Harris, et al.,[294] who observed pattern oscillations when GaAs growth was resumed on a tin-rich surface, and to Wood.[295] Since then RHEED oscillations have been observed with AlGaAs and Ge[296] and InGaAs[297] on GaAs substrates and recently RHEED oscillations for silicon on silicon[298][299] have been reported.
Two approaches to measuring intensity variations are shown in Fig. 16a. Examination of the specular beam in an off-Bragg condition reveals an increased sensitivity to the step density (and terrace width). A minimum in intensity corresponds to a maximum density of surface steps. The oscillations damp with time at a rate depending on the initial surface conditions and the final step density. One period of oscillation corresponds to the growth of one monolayer (Ga + As). An illustration of specular beam intensity versus time when the gallium beam is exposed is shown in Fig. 16b. Since the gallium flux determines the growth rate under As-stabilized growth, the period of oscillation allows the gallium flux to be determined. Growth under Ga-stabilized conditions allows the arsenic incorporation...
