Dislocation etch‐pits revealed in submicron (100) GaAs epilayers by selective dissolution in the saturated GaSb melt

Abstract

It has iwon showed t h a t t h e saturated Ga-Sh melt when contacting with (100) GaAs sutntrate or a thin f i l i i i selectively dissolves these solid phases. T h e dissolved thickness can br tiiitde so small as 500 A and t h e revealed etch-pits a r e corresponding to t h e c,ntrrtnces of tlislocation lines on t h e cxarriined surface. I t has been showed by one of the authors (BOLKHOVITYANOV 1981(BOLKHOVITYANOV , 1982a) that a 111-V substrate has t o be dissolved in a saturated multicomponent liquid of the same 111-V system if the lattice constant of the equilibrium solid differs from that of the substrate. IAet us indicate the lattice parameters of an investigated solid and the solid equilibrium liquid of which is used for contact as a, and uG correspondingly. So, if u, < (lo the etch-pits have been discovered on different 111-V substrates after their exposure in different 111-V liquids (BOLKHOVITYANOV 1982 b). I n that paper we used the substrates of the { 111) R orientation in major of causes. In this work the general attention is dlrected t o the discovery of the etch-pits on the (100) GaAs solid and it is shown that these etch-pits have a dislocation nature. I n the literature we can find the examples of different chemical etchants which reveal the dislocation etch-pits on the (100) orientation of Ga.4~ (for example, A B etchant (ABRAIIAMS, B~JIOCCHI)). However the etching rate of { 001) plane in A-B etchant is so fast that it is impossible t o use it to thin GaAs layers. The exception is t h e etching of GaAs into molten KOH (ISIIII et al.). The smollest removed thickness about 0.2 pm was announced in this work.The expected advantages of a selective melt dissolution of different films in the saturated non-equilibrium solution are: (i) extremely low thickness of etched semiconductor material with simultaneous development of an etch-pits clear image; (ii) the possibility of application of this method t o different 111-V semiconductors (BOLK-HOVITYANOV 1!)82 b).On the beginning this work we used the saturated In-As and Ga-Sb melts for the { IOO} GaAs plane. The first solution produced the very long etch-pits in a lateral direction (Fig. l a ) and was inconvenient. After that we used the second solution only and liquidsolid contact carried out a t 500 and 450 "C ( Fig. lb-f). The etch-pits looked like holes with obvious crystallographic facets if the saturated Ga-Sb melt was