Tetsuya Taki

Thermodynamic Analysis of InxGa1-xN Alloy Composition Grown by Metalorganic Vapor Phase Epitaxy

A thermodynamic analysis of alloy composition is described for metalorganic vapor phase epitaxy (MOVPE) of Inx Ga1-x N. The vapor-solid distribution relationship is discussed in comparison with the experimental data reported in the literature. It is shown that the solid composition of Inx Ga1-x N alloy grown by MOVPE is thermodynamically controlled. The origin of the deviation of the solid composition from the linear relation is also discussed.

Thermodynamic analysis of the MOVPE growth of InxGa1−xN

A chemical equilibrium model is applied to the growth of the In x Ga 1-x N alloy grown by metalorganic vapor-phase epitaxy (MOVPE). The equilibrium partial pressures and the phase diagram of deposition are calculated for the In x Ga 1-x N alloy. The vapor-solid distribution relationship is discussed in comparison with the experimental data reported in the literature. It is shown that the solid composition of the In x Ga 1-x N alloy grown by MOVPE is thermodynamically controlled and that the incorporation of group III elements into the solid phase deviates from a linear function of the input mole ratio of the group III metalorganic sources under the conditions of high mole fraction of decomposed NH 3 (high value of α), high temperature and low input V/III ratio. The origin of the deviation of the solid composition from the linear relation is also discussed.

Thermodynamic study on the role of hydrogen during the MOVPE growth of group III nitrides

Abstract The role of hydrogen during the MOVPE growth of group III nitrides is investigated from a thermodynamic point of view. The effect of hydrogen is reported for the driving force for the deposition of binary nitrides as functions of growth temperature and V/III ratio. The effect of hydrogen for the InGaN growth is discussed for the vapor–solid relationship, the formation of compositional inhomogeneity and input partial pressure of the group III elements. The difference between the growth reaction of the indium containing nitrides and that of other III–V compounds is also discussed.

Thermodynamic Analysis of Hydride Vapor Phase Epitaxy of GaN

A thermodynamic analysis of hydride vapor phase epitaxy (HVPE) is described for GaN. The partial pressures of gaseous species in equilibrium with GaN are calculated for temperatures, input GaCl partial pressures, input V/III ratios and mole fractions of hydrogen relative to the inert gas atoms. It is shown that the deposition of GaN is significantly influenced by the hydrogen mole fraction in the carrier gas. The growth rate is discussed in comparison with the experimental data reported in the literature. It is shown that the growth rate of GaN grown using HVPE is thermodynamically controlled.

Halogen-Transport Atomic-Layer Epitaxy of Cubic GaN Monitored by In Situ Gravimetric Method

In situ gravimetric monitoring (GM) of atomic-layer epitaxy (ALE) of cubic GaN on a GaN buffer layer/GaAs (001) is investigated using a halogen-transport system with GaCl and NH3 sources. The cubic GaN growth rate of one monolayer/cycle is obtained at a temperature ranging from 350 to 400°C. It is found that pure cubic GaN can be grown by halogen transport ALE. The growth rate decreases with increasing growth temperature, and a constant growth rate of about 0.45 is observed from 410 to 550°C. In this paper, it is shown that the in situ GM method is a powerful tool for understanding growth mechanism of the group III nitrides, as well as that of GaAs.

Substitution reaction of surface adsorbed P atoms to As atoms in the GaP/GaAs atomic layer epitaxy

The substitution reaction of surface adsorbed phosphorus (P) atoms to arsenic (As) atoms in the GaP/GaAs system is studied using a halogen transport atomic layer epitaxy (ALE) under an atmospheric pressure. The rate equations for the substitution reaction are led from the dependencies on the As4 exposure time and partial pressure. Based on the results, we propose a mechanism consisting of two kinds of substitution. It is shown that the substitution reaction of surface adsorbed P atoms to As atoms more rapidly occurs, compared with that of surface adsorbed As atoms to P atoms.

Atomic layer epitaxy of GaAs using GaBr and GaI sources

Abstract Halogen transport atomic layer epitaxy (ALE) of GaAs using GaBr and GaI is investigated by means of two in situ monitoring methods: the gravimetric method and the surface photo-absorption (SPA) method. It is shown that the growth of one monolayer/cycle is possible in both the GaBr and GaI systems under a wide range of growth conditions at low temperature, while at high temperature, the decrease of the growth rate is observed due to the weak adsorption force of GaBr and GaI on GaAs surface. In addition, in both methods, we have observed the slow rate of HBr desorption during H 2 purge after GaBr supply in comparison with the GaCl system. The reaction mechanism that proceeds on the GaAs surface in GaBr and GaI sources is discussed.

In situ monitoring of hydrogen adsorption on (001) Ga surface in GaAs atomic layer epitaxy

Abstract In situ monitoring of the growth process in atomic layer epitaxy (ALE) is essential for understanding the growth mechanism. In the present paper, investigation of the chemisorption of hydrogen atoms on the (001) GaAs surface in an atmospheric pressure halogen transport ALE using the surface photo-absorption (SPA) method is reported. Furthermore, the Ga surface is monitored using temperature-programmed desorption (TPD) with SPA. It is shown that Ga atoms on the (001) surface react with and are terminated by hydrogen in the carrier gas and the desorption from the surface occurs by the reverse reaction in the inert carrier gas. The occurrence of these reactions is confirmed by the Langmuir equation of the dissociative isotherm.

Investigation of Arsenic Desorption from GaAs (111) B Surface in Atmospheric Pressure Atomic Layer Epitaxy

Arsenic desorption from the GaAs (111)B surface is investigated under atmospheric pressure using an in situ gravimetric monitoring system, which is equipped with a halogen transport atomic layer epitaxy (ALE) reactor and a microbalance system. It is shown that the growth rate decreases from > 1.0 to 0.5 molecular layer (ML)/cycle with increasing H2 purge time after AsH3 supply depending on the As coverage on the surface, and (111)B GaAs has three kinds of reconstructed surfaces in the atmospheric ALE. The atomic force microscopy (AFM) images of 100 ML grown surfaces show that atomically smooth surfaces can be obtained on the reconstructions of (1×1)LT and (√19×√19).

In Situ Monitoring of the Chemisorption of Hydrogen Atoms on (001) GaAs Surface in GaAs Atomic Layer Epitaxy

We study the chemisorption of hydrogen atoms on the (001) GaAs surface in an atmospheric pressure halogen transport ALE using the surface photoabsorption (SPA) method. The dependence of the SPA signal on the H2 partial pressure on the (001) Ga surface is investigated at 450° C. Furthermore, the Ga surface is monitored using temperature-programmed desorption (TPD) with SPA. It is shown that hydrogen in the carrier gas reacts dissociatively with Ga atoms on the (001) surface, and the desorption of hydrogen occurs by the reverse reaction in the inert carrier gas. The occurrence of these reactions is confirmed by the Langmuir equation of the dissociative isotherm.