New mechanisms in photo-assisted MOVPE of II-VI semiconductors

Abstract

The first detailed comparison has been made of the metalorganic vapor phase epitaxy growth rates of CdTe, ZnTe, and ZnSe, measured in situ with laser reflectometry. The comparison also includes the photo-assisted growth with visible radiation from an argon ion laser. Using a standard Group II precursor (DMCd or DMZn.TEN) partial pressure of 1.5 x 104 atm, VI/II ratio of I and DIPM (M = Te, Se) the maximum growth rates are in the region of 10 to 15 AU/ s. Decrease in growth rates of ZnTe at higher temperatures or higher laser powers have been attributed to the desorption from the substrate of unreacted Te precursor. The behavior of DTBSe is quite different from DIPSe for both pyrolytic and photo-assisted growth. The maximum growth rate is around 1 AU/ s with very little photo-enhancement, except at 300~ Secondary ion mass spectroscopy analysis of hydrogen concentration in the ZnSe layers shows high concentrations, up to 5.9 x 1019 atoms cm 3 for DTBSe grown ZnSe under pyrolytic conditions. These results show that the growth kinetics play an important part in the incorporation of hydrogen and passivation of acceptor doped material.

Hydrogen effusion from epitaxial ZnSe layers grown by metalorganic vapor phase epitaxy

“…We suggest that the detected hydrogen originates mainly from pyrolysis products of the precursors. This suggestion is well supported by the results of Irvine et al 7 who showed that the hydrogen concentration in the samples varies considerably with the choice of precursors. In the present experiments a pronounced influence of the growth stoichiometry ͑Fig.…”

The kinetics of the growth of nitrogen-doped ZnSe grown by photo-assisted MOVPE

“…4 The concentrations of organometallics entering the reactor were measured using an Epison monitor and the growth rate and layer thickness measured in situ using laser interferometry. 4 The concentrations of organometallics entering the reactor were measured using an Epison monitor and the growth rate and layer thickness measured in situ using laser interferometry.…”

“…4,8 All these experiments were performed at 1:1 precursor VI:II ratio. This has been attributed to the decrease in beta hydrogen elimination, along with an increase in free radical mediated decomposition, with less steric hindrance for insertion of free radicals into the Se precursor.…”

“…This precursor also has the property that there are no N-H bonds, as is the case for tBNH 2 , and indications are that the (CH 3 ) 3 Si radical will cleave cleanly leaving N on the surface. The growth rate depends on the surface coverage of DMZn and DESe along with their reaction rate which is given by the constant, K. GR = Kθ DMZn θ DESe (4) where GR is the growth rate, θ DMZn and θ DESe are the surface coverage factors for the precursors DMZn and DESe, respectively. 6.…”