A novel approach towards reduced growth temperatures and hydrogen incorporation in the MOVPE of ZnSe, ZnS and ZnSSe for blue LEDs and lasers

We report on the atmospheric pressure MOVPE growth and characterisation of ZnSe, ZnS and ZnSxSe1-x, (0.095<x<0.629) epilayers; on (100)GaAs by using a novel class of VI-group alkyls of the form R2X2 (where X=Se, S and R=Et, Me). These precursors allowed to reduce the growth temperatures of pyrolytic MOVPE by almost 150°C with respect to the more common R2X alkyls. Growth temperatures below 400°C were achieved. Calibrated secondary ion mass spectrometry (SIMS) analysis carried out on ZnSe epilayers grown by Me2Se2 showed [H] around (1-3)x10^(17) cm^(-3), i.e. amongst the lowest ever reported for MOVPE-grown ZnSe. Mechanisms that explain these findings are briefly discussed. Cl and I incorporation in ZnSe were also evaluated by SIMS and indicated overall residual concentrations <6x10^(15) cm^(-3). The structural properties of ZnSe and nearly lattice-matched ZnSSe epilayers were assessed by double-crystal Xray diffraction measurements. 5K cathodoluminescence showed the good optical quality of as-grown ZnSe, further confirming the results of SIMS analysis.