Observations on Si Contamination in GaP LPE

Abstract

Silicon has long been known to be an unintentional impurity often present in ; however, the concentration of the Si and its effects have not been known. It has been observed that the net donor concentration in undoped LPE layers fluctuates from for different growth runs when growth is in ∼1 atm of . This background is attributed to unintentionally present Si donors. The Si concentrations in these as well as S‐ and Zn‐doped layers as determined by ion microanalyzer measurements range from with the typical value being . In the undoped layers often exceeds . The variations in both background and are attributed to variations in the oxygen level of the gas ambient which is inversely related to the . An important reaction resulting in Si contamination is reduction of the quartz used in the construction of the LPE growth system. With a growth sequence designed to grow both a Zn‐ and oxygen‐doped p‐layer onto an undoped n‐layer in the same growth run, precipitates have been observed in the p‐layer near the p‐n junction. The identification of these precipitates as is further proof of the high levels of Si contamination that can occur during LPE growth. Minority carrier lifetimes for Si‐doped LPE layers with are considerably longer than have been obtained by doping with S or Te. The increased lifetime is attributed to either a reaction involving Si which results in the reduction in the concentration of an important nonradiative center or the fact that the usual dopants S and Te themselves are involved in a nonradiative center.