- •ACKNOWLEDGMENTS
- •TABLE OF CONTENTS
- •LIST OF TABLES
- •LIST OF FIGURES
- •INTRODUCTION
- •2.1.1 Structural Properties
- •2.1.2 Physical Properties
- •2.1.3 Electrical Properties of InN
- •2.1.3.1 Background Defects
- •2.1.4 Optical Properties of InN
- •2.2.1 Thermodynamic Models in Solid Solution
- •2.2.1.1 Regular Solution Model
- •2.2.1.2 Bonding in Semiconductor Solid Solutions Model
- •2.2.1.4 Strain Energy Model
- •2.2.1.5 First-Principal Models
- •2.2.2 Thermodynamic Analysis of InN
- •2.2.3 Phase Separation in InxGa1-xN
- •2.3.1 Growth Temperature and V/III Ratio
- •2.3.2 Nitrogen Source
- •2.4 Indium Nitride (InN) Growth Techniques
- •2.4.1 Chemical Vapor Deposition (CVD)
- •2.4.1.1 Metal-Organic Vapor Phase Epitaxy (MOVPE)
- •2.4.1.2 Hydride Vapor Phase Epitaxy (HVPE)
- •2.4.1.3 Plasma Enhanced Chemical Vapor Deposition (PECVD)
- •2.4.3 Atomic Layer Deposition (ALD)
- •2.5 Substrate Materials
- •2.5.1 Sapphire Substrate (Al2O3) (0001)
- •2.5.2 Silicon (Si) Substrate
- •2.5.4 Other Substrates
- •2.5.5 Buffer Layer
- •2.6 Summary for Growth of InN on Different Substrate
- •2.6.2 Growth on Silicon (Si) Substrate
- •2.6.3 Growth on Gallium Arsenide (GaAs) Substrate
- •2.6.4 Growth on Gallium Phosphorus (GaP) Substrate
- •2.7 Overview
- •THERMODYNAMIC ANALYSIS OF InN AND InXGa1-XN MOVPE GROWTH
- •3.1 Thermodynamic Analysis of InN and InxGa1-xN
- •3.1.1 Reaction Mechanism and Kinetics of InN MOVPE
- •3.2.1 Boundary Passivation Method with Hydrogen
- •5.1. Indium Nitride (InN) Growth Optimization
- •5.1.1. Substrate Selection
- •5.1.1.1. Sapphire (c-Al2O3 (0001))
- •5.1.1.2. Gallium Nitride (GaN/c-Al2O3 (0001))
- •5.1.1.3. Silicon (Si (111))
- •5.1.2. Substrate Preparation Procedure
- •5.1.3. Metal-Organic Vapor Phase Epitaxy (MOVPE) Reactor
- •5.1.4. Growth Chemistry and Conditions for InN Growth
- •5.1.5. Indium Nitride (InN) Growth and Optimization
- •5.1.5.1. Influence of Growth Temperature
- •5.1.5.2. Influence of Substrate Nitridation
- •5.1.5.3. Influence of N/In Ratio
- •5.1.5.4. Influence of Buffer Layer and Morphological Study
- •5.1.5.5. Influence of Pressure
- •5.1.5.6. Optical and Electrical Properties
- •5.1.5.7. Summary
- •5.1.6. Indium Nitride (InN) Droplet Formation
- •5.1.7. Annealing Effect
- •5.3. Inlet Tube Modification and Growth Results
- •CONCLUSIONS
- •LIST OF REFERENCES
- •BIOGRAPHICAL SKETCH
57
indium chloride is formed at the temperature higher than 750 oC. Furthermore, it was necessary to exclude H2 from the reaction system for deposition to occur because the high partial pressure of H2 increases the amount of InCl. These results indicate that the effective chemical substance of indium chlorides for the growth is InCl3. Growth rate of 1.5 µm/h was obtained at 570 oC and single crystalline InN growth was confirmed by X- ray diffraction measurement [Sun96].
The growth of InN using MOVPE and HVPE was discussed in terms of growth conditions. For MOVPE, the structure of InN depends on the nitridation temperature for GaAs(111)B substrates. For HVPE, InCl3 forms InN film more effectively than InCl does.
2.6.4 Growth on Gallium Phosphorus (GaP) Substrate
Guo et al. reported that InN films had been grown on GaP (111) substrate at 500 oC using microwave-excited MOVPE and TMI and nitrogen were used as the source materials. The epitaxial InN film was obtained on GaP (111) by exposing the substrate to the nitrogen plasma for 60min before growth [Guo95b]. InN films have a wurtzite structure [Guo95b].
Bhuiyan et al. obtained InN on GaP(111)B by the horizontal MOVPE reactor where single crystalline InN films can be obtained on GaP(111)B only when the nitridation of the substrate is not made intentionally. InN films grown on nitrided GaP(111)B are found to be polycrystalline. XPS analysis shows the formation of PNx as well as GaN after the nitridation of GaP (111)B substrate surfaces by flowing NH3 above 500 oC. Formation of PNx is responsible for the poor crystalline structure for InN. A single crystalline InN film with an excellent surface morphology can be grown on
58
GaP(111)B at high temperature (600-650 oC) using a low temperature InN buffer layer [Bhu00a,Bhu01,Bhu02b].
The growth of InN on GaP substrate using MOVPE was briefly discussed. When the growth of InN is performed on GaP substrate, the nitridation step should not be required in order to obtain the single crystalline InN.
2.6.5Growth on Gallium Nitride (GaN) and Alumimum Nitride (AlN) Substrate
Yamaguchi et al. presented the result of the InN film grown on GaN substrate with
AlN buffer layer using atmospheric MOVPE. Growth temperature was 450 oC and V/III ratio was 105. The FWHM of XRC decreases with increasing the thickness of InN film [Yam99a].
The effects of reactant-gas velocity on the growth of InN on GaN/sapphire by MOVPE were studied by Yang et al. With a high-speed reactant gas, the thickness of the stagnant layer is reduced so that the reactant species can reach the surface effectively. A layer like growth of InN was achieved, resulting in a significant improvement of the film quality. In addition, significant enhancement of the growth rate up to 2 µm/h was obtained. The FWHM of XRC decreased with increasing gas velocity. FWHM of XRC for InN (0002) with 476 arcsec was reported but there was no report about whether the InN is single or poly crystalline [Yan02a].
The possibility that high quality single crystalline InN can be grown on GaN/sapphire substrate using MOVPE is studied and it is found that the flow pattern of source materials can have an effect on the InN film quality.