Features of the Vapor-Phase Epitaxy of GaAs on Nonplanar Substrates
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INTERNATIONAL SYMPOSIUM “NANOPHYSICS AND NANOELECTRONICS”, NIZHNY NOVGOROD, MARCH 10–13, 2020
Features of the Vapor-Phase Epitaxy of GaAs on Nonplanar Substrates Yu. N. Drozdova,*, S. A. Kraeva, A. I. Okhapkina, V. M. Daniltseva, and E. V. Skorokhodova a Institute
for Physics of Microstructures, Russian Academy of Sciences, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received April 15, 2020; revised April 21, 2020; accepted April 21, 2020
Abstract—The features of the surface shape of GaAs epitaxial layers grown on grooves several micrometers wide with vertical walls and an aspect ratio close to unity are investigated. The grooves are formed on the surface of a GaAs wafer in a plasma-chemical etching installation and overgrown by organometallic vapor-phase epitaxy under reduced pressure in a reactor. Keywords: plasma-chemical etching of GaAs, narrow grooves, epitaxy of GaAs in grooves DOI: 10.1134/S1063782620090080
1. INTRODUCTION Long grooves on a GaAs surface with a depth and width of several micrometers can be the basis for creating a number of semiconductor devices if the grooves are filled with an epitaxial GaAs layer of one doping type and created in a GaAs layer of a different doping type. In particular, designs of horizontal and vertical transistors, which use two p–n junctions formed on the walls of a narrow groove, have been patented. Nowadays, GaAs technology is well developed but, conventionally, it represents planar layer-by-layer growth. It is much more difficult to overgrow narrow grooves, which hinders the development of industrial technologies. Many features arise, but in the present study, main attention is paid to the morphology of the growth front inside the groove and along its edges. From published data, it is known that narrow grooves on the surface of GaAs(001) can be obtained by chemical [1] or plasma-chemical etching [2]. For subsequent epitaxial growth, chemical etching is preferable because it forms a minimal damage layer. However, the slope of the walls during chemical etching substantially depends on the direction of the grooves. The greater stability of the (111)Ga surfaces as compared with (111)As manifests itself in the fact that the grooves deposited along the [ 110] direction narrowed in depth, whereas those deposited along the [110] direction expanded [1] as is shown in Fig. 1. Our preliminary experiments on the liquid-phase etching of the grooves confirmed the pattern shown in Fig. 1. Diagonal grooves between the directions shown in Fig. 1 may have the walls close to vertical, but liquid-phase etching leads to unacceptable lateral expansion due to mask underetching. Mask underetching prevents obtaining deep and, at the same time, narrow
grooves necessary for transistors. The plasma-chemical etching method turned out to be more suitable. In this study, we investigate the surface shape of GaAs epitaxial layers grown on grooves of several micrometers wide with vertical walls and an aspect ratio close to unity. Main attention is paid to the initial stage of overgrow
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