Etching of germanium surfaces prior to evaporation of aluminum

Claim 1

IN THE PROCESS OF FORMING A JUNCTION TRANSISTOR COMPRISING THE STEPS OF HEATING A P-TYPE GERMANIUM WAFER IN ARSENIC VAPOR FOR A TIME AND AT A TEMPERATURE TO FORM AN N-TYPE ARSENIC-FIFFUSED SURFACE ZONE, ALLOYING ALUMINUM INTO A SELECTED PORTION OF THE ARSENIC-DIFFUSED SURFACE ZONE FOR CONVERTING SAID PORTION TO P-TYPE, AND FORMING AN EMITTER CONNECTION TO SAID ALUMINUM ALLOYED PORTION, A BASE CONNECTION TO THE ARSENIC-DIFFUSED SURFACE ZONE AND A COLLECTOR CONNECTION TO THE ORGINAL P-TYPE PORTION OF THE WAFER, THE IMPROVEMENT COMPRISING IN COMBINATION THEREWITH SUCCESSIVELY ETCHING THE ARSENIC-DIFFUSED GERMANIUM WAFER WITH A DILUTE SOLUTION OF HYDROGEN PEROXIDE, HAVING A CONCENTRATION WITHIN THE RANGE OF 2 TO 5 PERCENT, AT A TEMPERATURE WITHIN THE RANGE OF 20* TO 50* C., AND SUBJECTING THE SAID WAFER TO VACUUM SUBLIMATION PRIOR TO ALLOYING ALUMINUM INTO THE ARSENIC DIFFUSED LAYER.