Amorphous chalcogenide semiconductors are generally ptype semiconductors and added impurities do not alter their conduction type. For development and characterisation of new amorphous semiconducting materials for their diverse technical applications, it is important that their electronic properties and microstructures should be well understood. Further, it should be possible to make them n/p type in acontrolled way. In this context Ge Ml. (M=S, Se, Te) glasses are unique amorphous semiconductors which exhibit p—n transition in their electronic conduction wnen modified with large concentration of Bi impurity (11 at%, 7 at% and 3.5 at% Bi in Ge—S, Ge—Se and Ge—Te respectively (1,2,3). We have recently been investigating this new class of materials to understand their unique properties (1,4,5). In this talk I would present a brief account of some our recent - findings on the semiconductors in the system Ge-S-Bi. Among the amorphous Ge-M, (M=S, Se, Te) semiconductors, the system GeXS1.X occupies a unique position. In the qlassy form these alloys have short range order which is dependent upon value of x and is quite different from that in the corresponding crystalline form (6) Further, this is the only system among the chalcogenide glasses which exhibits ESR signal under ambient conditions.