NEW MECHANISMS IN PHOTO-ASSISTED MOVPE OF II-VI SEMICONDUCTORS

The first detailed comparison has been made of the metalorganic vapor phase epitaxy growth rates of CdTe, ZnTe, and ZnSe, measured in situ w ith laser reflectometry. The comparison also includes the photo-assist ed growth with visible radiation from an argon ion laser. Using a stan dard Group II precursor (DMCd or DMZn.TEN) partial pressure of 1.5 x 1 0(-4) atm, VI/II ratio of 1 and DIPM (M = Te, Se) the maximum growth r ates are in the region of 10 to 15 AU/s. Decrease in growth rates of Z nTe at higher temperatures or higher laser powers have been attributed to the desorption from the substrate of unreacted Te precursor. The b ehavior of DTBSe is quite different from DIPSe for both pyrolytic and photo-assisted growth. The maximum growth rate is around 1 AU/s with v ery little photo-enhancement, except at 300 degrees C. Secondary ion m ass spectroscopy analysis of hydrogen concentration in the ZnSe layers shows high concentrations, up to 5.9 x 10(19) atoms cm(-3) for DTBSe grown ZnSe under pyrolytic conditions. These results show that the gro wth kinetics play an important part in the incorporation of hydrogen a nd passivation of acceptor doped material.