GAS-SOURCE MOLECULAR-BEAM EPITAXY OF ZNSE USING ELEMENTAL ZN AND HYDROGEN SELENIDE

We report the growth of unintentionally doped ZnSe by gas-source molecular beam epitaxy using elemental Zn and thermally cracked hydrogen selenide (H2Se). The dependence of the growth rate on H2Se flow rate indicates that the minority source flux limits the growth. The stoichiometric growth condition is established. It is found that the two-dimensional growth regime of ZnSe films a extends down to 150 degrees C. The electrical and optical properties of ZnSe epilayers are characterized by Hall and photoluminescence measurements. Undoped ZnSe epilayers show n-type conduction with an electron concentration of 1.6x10(16) cm(-3) and Hall mobility of 490 cm(2)/V s at room temperature. Low-temperature photoluminescence spectra of undoped ZnSe epilayers are dominated by neutral donor-bound exciton emission located at 2.7968 eV. The residual donor impurities of In and Cl are detected in ZnSe epilayers by secondary-ion-mass spectroscopy measurements and are responsible for the n-type conduction. It is confirmed that the donor impurities originate from the H2Se gas source. (C) 1995 American Institute of Physics.