Growth and Characterization of Indium Gallium Phosphide on Gallium Arsenide by Gas Source Molecular Beam Epitaxy System and Its Applications to Heterostructures PDF Download

Author: Dhrubes Biswas
Publisher:
ISBN:
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Languages : en
Pages : 192

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Book Description
InGaP/GaAs system presents an attractive alternative to GaAs/AlGaAs system for heterojunction devices because of its unique heterojunction properties, wide band gap of about 1.90 eV for the lattice matched composition and absence of oxidation problems typical for AlGaAs. However, the growth of InGaP requires the use of phosphine, which necessitated the use of Gas Source Molecular Beam Epitaxy (GSMBE). The gases involved are very hazardous, extremely toxic, highly inflammable and explosive at elevated temperatures. Adequate care has been taken for the safe use of these gases so that this attractive technique is properly utilized. The GSMBE system is equipped with a central alarm command system with audio-visual alarms for a variety of monitored conditions and interlocks for automatic shutdown. Samples studied were grown on (100) GaAs substrates under various growth conditions. Reproducible growth conditions have been established with respect to optimisation of pressure and temperature so as to achieve good material properties. Structural characterization using X ray has been carried out for the determination of material composition and evaluation of crystal quality. Very narrow full width at half maxima values indicated good crystal quality. Additionally, cross-sectional TEM has shown smooth heterointerface. Subsequent to this, good hall mobility at room temperature and at 77K, confirmed the material quality. Photoluminescence has been utilized for the evaluation of the E$\sb0$ gap. The PL exhibited very narrow full width at half maxima for lattice matched composition. Apart from evaluation of the E$\sb1$ gap, spectroscopic ellipsometry has been used to investigate the compositional dependence of the E$\sb1$ gap (and its broadening). P-type modulation doped heterostructures has been implemented using InGaP/GaAs, demonstrating two dimensional hole gas (2DHG) with good p-type hole mobilities measured from room temperature up to very low temperatures. The approximate constant value of mobility in the low temperature region strongly confirms the presence of 2DHG. A simple model has been formulated for the estimation of valence band discontinuity from the measured 2DHG data at cryogenic temperatures. Heterostructure Bipolar Transistor has been demonstrated using InGaP/GaAs system with the realisation of good current gain and low offset voltages. The double heterostructure bipolar transistor showed even smaller offset voltages. The classical V$\sb{CE}$ versus I$\sb{c}$ plots and gummel plots for the devices shows an ideality factor close to unity for I$\sb{c}$ and other usual characteristic features.