Nonlinear optical diagnostics of a crystalline film in molecular-beam-epitaxy devices

ABSTRACT A new method of film structure monitoring is proposed. It is based on the analysis of second harmonic (SH) radiation induced in a film irradiated by a laser beam. 511 intensity measurement versus angle of the plane of polarization of the incident light and versus film thickness provides the information about film crystal quality,presence of polycrystalline component and crystallographic axes orientation. This method can be complementaryto the well- known ones and is supposed to be especially suitable for research groups since it allows a correlationbetween technological and crystallographic parameters to be quickly determined. 1. INTRODUCTION The films used in semiconductor industry now must have an extremely high quality. Hence it is principallyimportant to control crystalline quality of the films. Modern high-vacuum facilities (HVF) make it possible to growup heterostructures with new physical properties. However, a successful growth of structures is only possible withthe use of effective means of diagnostics and control. This is due to very high requirements to homogeneity andthickness of heterolayers on the one hand, and high sensitivity of the growth itself to the growth conditions on theother one. It is desirable to widen the scope of diagnostics means. In this paper the authors discuss laser nonlinearoptical diagnostics of a crystalline quality of films. The use of laser radiation for diagnostics is very attractive interms of technology. It is consistent with high-vacuum systems, compatible with the existent production lines, doesnot demand change in design of available facilities, does not affect film growth, etc.For the structures of the A2B6 and A3B5 types, being of most interest and their based solid solutions a linearrefractive index is isotropic and insensitive to a crystalline structure, so it is difficult to use control methods basedon the linear optic.We have suggested' to use for diagnostics the 511 signal, generated in a film by laser radiation. In the films