Investigation of ohmic and Schottky contacts on n-GaAs using spin-on glass capping layers and scanned electron beam alloying

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Abstract
A thin spin-on glass film has been used as a cap during alloying of concentric Au-Ge/Ni ohmic contacts to n-GaAs. Both furnace and scanned electron beam (SEB) capped alloyed contacts exhibit approximately a factor of 4 to 5 times lower specific contact resistance and a significantly improved surface morphology compared with that of uncapped alloyed contacts. Electrical measurements of Schottky diodes formed on GaAs surfaces which have been exposed to the alloying process reveal that the spin-on glass capped surfaces are better preserved than the uncapped surfaces. SEB alloyed contacts (both uncapped and capped) exhibit good resistance to degradation after 1000 hours of aging at 200 degrees C. Furthermore, Schottky diodes formed on capped SEB alloyed surfaces exhibit the least change in their electrical parameters during aging at 200 degrees C.