Low temperature grown Be-doped InAlP band offset reduction layer to p-type ZnSe

To solve the difficulty of achieving a low resistance ohmic contact to p-type ZnSe, the use of an intermediate p-type InAlP layer to p-type ZnSe as a valence band offset reduction layer is studied by gas source MBE (molecular beam epitaxy). It is found that the surface morphology of the In_0.5Al_0.5P layers grown on (001) ZnSe becomes better as the growth temperature is decreased. The further use of the group III-flux modulated growth method produces a better surface morphology. It is found that the hole concentrations as high as 2×10¹⁸ cm^-3 are easily obtained for p-type InAlP layers grown even at low temperature of 350°C, although a higher Be cell temperature is required than that for a 500°C grown p-type InAlP due to decreased electrical activity of Be in InAlP. Despite the very high Be concentrations, the Be precipitation/segregation is not observed. These results suggest that the Be-doped InAlP layer can be used as an intermediate layer to form the low resistance ohmic contact to p-type ZnSe