Preparation of low dislocation density and semi-insulating Indium Phosphide using LEC technique

Indium Phosphide is a semiconductor which is very useful for applications in the field of micro and optoelectronics. Growth of InP bulk single crystals by Liquid Encapsulation Czochralski (LEC) is stil a major problem of scientific and technological importance. The lack of a suitable dopant to reduce the EPD without enhancing the number of free carrier concentration has been eliminated by the addition of codopants, namely Cadmium and Sulplhur. In the present work, it will be shown that it is possible to obtain LEC boules having n-type conductivity over the entire crystal length with a distribution of carriers more homogeneous than in crystals doped, for instance with sulphur alone. The doping procedure adopted leads to a good evaluation of the segregation coefficient of Cadmium in InP. The coefficients reported in the literature are so scattered that it is difficult to set accurately the amount of dopant to be added for obtaining the desired doping level. A variety of dopants have been made use of to understand the nature of dopants and their role in the structural and electrical characteristics of the crystal. The need of the hour is for good quality semi-insulating crystal which can be obtained through the addition of a suitable dopant. The problems involved with the addition of dopants for obtaining semi-insulating nature are presented. The determination of dopant concentration by a nondestructive method is discussed.