Studies of liquid-phase deposition-oxide/InP structure by liquid-phase deposition

Abstract

INTRODUCTIONElectrically insulating films with a low density of interfacial-electronic states are important for the development of metal-oxide semiconductor (MOS) technologies using indium phosphide (InP), a material showing good promise for high-speed devices and microwave and monolithic optoelectronic circuits. High-electron mobility and high-saturation velocity are the two key properties that make InP attractive for these applications. Metal-insulator semiconductor (MIS) interfaces formed on InP enjoy a surface-state density less than that of other III-V semiconductors studied to date. Early efforts focused on the development of InP MIS technology using anodic and thermal 1,2 oxides as gate insulators. However, the use of such oxides was abandoned because of their low resistivity and large amount of interface state. Thus, the best InP MIS results have been achieved with deposited dielectric layers. 3,4 Silicon dioxide (SiO 2 ) has been the most widely used gate dielectric in InP metal-insulator semiconductor field-effect transistors (MISFETs) because of its high quality and ease of deposition at moderate temperatures. Recently, chemical-vapor deposition (CVD) of SiO 2 onto InP 5-9 has been reported to provide usable MOS characteristics, while SiO 2 on GaAs has yielded only marginal results. 10-13 The attainment of good quality insulating films by traditional technologies usually requires elevated temperatures, but the volatile InP surface 14 requires that the substrate temperature remain as low as possible. Liquid-phase deposition (LPD) provides an alternative method of SiO 2 deposition. The LPDSiO 2 deposition is superior to alternative methods in terms of the following characteristics: 15 low-processing temperature, simple equipment, high-growth rate, selective deposition, low cost, and high film quality. In our previous studies, 12,16 the LPD-SiO 2 films were successfully deposited on Hg 1-x Cd x Te and GaAs. In this paper, we extend our prior work by using LPD to deposit SiO 2 films on InP. Thus, a detailed investigation of the technique, growth mechanism, and film qualities for LPD deposition of SiO 2 on InP is presented. EXPERIMENTAL PROCEDUREApparatus and basic LPD equilibrium equations are found in our previous study. [11][12][13]17 The starting solution is a commercial 34 wt.% hydrofluosilicic (H 2 SiF 6 ) solution from which a 3.09 M H 2 SiF 6 saturated-growth solution is prepared. Excess silicicacid powder (SiO 2 ϫ H 2 O), instead of a previous study's SiO 2 powder, 18 is added to the starting solution and thoroughly mixed by stirring for 6 h at room temperature. To ensure solution saturation, H 2 O 2 is added to the solution, and the color of the soSilicon-dioxide (SiO 2 ) growth on an indium-phosphide (InP) substrate by use of room-temperature (ϳ30°C) liquid-phase deposition (LPD) is demonstrated. The produced LPD-SiO 2 is of good quality and reliability because of the suppression of interdiffusion by use of relatively low temperatures. Because LPD is difficult without residual OH on the substrate...