As-grown surfaces of AlGaAs/GaAs/AlGaAs heterostructures were stuck down the glass disks and after that the GaAs substrates were removed completely by selective chemical etching. As a result the back-surface of the heterostructures became open to light. The influence of different factors on the back-surface planarity and on the density of such specific defects as holes in the GaAs layer have been investigated. It is shown that the density of holes can be decreased to a value less than 1 holelcm' if a glove-box maintained under a pure N, atmosphere and connected with LPE installation is used.The heterostructures (HS) based on AlGaAs solid solutions and grown on GaAs wafers sometimes have to be employed without substrates, for example, in solar cells (ALFEROV et al.). First of all the as-grown surface of such heterostructure is stuck down the transparent substrate, for example, down the glass one. Then the GaAs substrate is completely removed by the selective chemical etchant utilizing the well-known etching process (LE PORE). As a result the interface between the GaAs wafer and the first AlGaAs film (i.e. the back-surface of the heterostructure) comes to light. Such a new structure can be used for different applications.The present study is devoted to morphological investigations of the back-side of the AlGaAs/GaAs/AlGaAs heterostructures grown on the GaAs (1 00) substrates (tin-doped, n -10" ~m -~) by liquid phase epitaxy (LPE). The main aims are the improvement of the planarity of these surfaces and minimization of the defects, the general type of which are the holes in the GaAs layer of the heterostructures appeared because of etching. This work has been fulfilled during the last few years and the results of the successive improvements of the LPE growth technique are summarized in the paper. In spite of these improvements in general described in the literature (except optimized chemical treatment of GaAs substrate) we belitwe that it would be useful to consider in detail the effect of certain LPE-process components on the quality of such specific heterostructures as the AlGaAs/GaAs/AlGaAs ones free crf supporting GaAs substrates.The AlGaAsJGaAsJAlGaAs heterostructures were grown by the method of contact replacement <>f liquid solutions (BOLKHOVITYANOV, a). Then, the as-grown surfaces of the 23 x 23 mm2 samples were stuck down the glass disks and the GaAs substrate was etched striping the AlGaAs surface. After that the heterostructures were investigated with an optical microscope in reflection and transparent modes.For the improvement of the first AlGaAs film quality the GaAs buffer layer is frequently grown and the undersaturated Ga -As liquid is usually used for the preliminary cleaning the substrate. This liquid slightly dissolves the GaAs wafer before the film growth will start. But such a dissolution distorts the substrate surface. The more significant increase
