Title

Photoassisted MOVPE growth of ZnSSe and ZnMgSSe on GaAs substrate, and simulation and fabrication of HBT's and solar cells

Date of Completion

January 1999

Keywords

Engineering, Electronics and Electrical|Engineering, Materials Science

Degree

Ph.D.

Abstract

This thesis describes the growth of high quality ZnSe, ZnSSe, and ZnMgSSe epitaxial films on GaAs substrates using photoassisted metalorganic vapor phase epitaxy (MOVPE). Ethyl iodide and hydrogen chloride were used as n-type dopant sources. A higher value of electron concentration was observed using hydrogen chloride (5.4 × 1018 cm-3 and 0.0070 Ω-cm, respectively), as compared to ethyl iodide (1.65 × 1018cm-3, and 0.067 Ω-cm, respectively) for ZnSe doping. Growth rate depression was observed to be more severe for iodine doped layers than for chlorine doped layers. Thus, it appears that hydrogen chloride is a superior dopant source for low temperature photoassisted MOVPE ZnSe growth of n-type layers for blue green laser diodes in the pressure-temperature regime investigated. ^ In the case of epitaxial ZnSyS1-y grown by photoassisted MOVPE on GaAs, we have shown for the first time lattice matched ZnSSe films on GaAs substrates using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butyhnercaptan (t-BUSH) as precursors. We have obtained sulfur compositions (y), ranging from 0 to unity (ZnS). The growth rate of the ZnS was 1μm/hr, which was previously unattainable using diethylsulfur (DES). The lattice matched sample (y = 0.07) showed a near band edge peak intensity (NBE) to deep level emission (DLE) ratio of 77 to 1, as determined by room temperature photoluminescence measurements. In comparison to DES we have shown that t-BUSH yields better NBE/DLE ratios and a significant increase in S incorporation. In the case of ZnMgSSe layers, we have obtained good crystal quality (FWHM of latticed matched Zn.94Mg.06S.11Se.89 equal to 50 arcseconds) and optical quality NBE/DLE ratios of greater than one. ^ We have also shown for the first time simulated ZnSe/GaAs HBTs using FEM technique and found that the ft of ZnSe/GaAs HBTs compare to AlGaAs HBTs, thus indicating the ZnSe/GaAs PIN photo-detectors could be integrated with ZnSe/GaAs HBTs, for high frequency integrated optoelectronics. We have also fabricated for the first time ZnSe/GaAs solar cells, by the photoassisted MOVPE growth technique. ^