SEMICONDUCTOR CHARACTERIZATION BY SCANNING FORCE MICROSCOPE SURFACE PHOTOVOLTAGE MICROSCOPY

A technique is described for the measurement of surface photovoltage (SPV) on semiconducting samples using the attractive-mode scanning force microscope. The use of SFM potentiometry1 permits microscopic measurement of surface photovoltage to be made in air with a spatial resolution of a few tens of nm and voltage resolution of better than 1 mV. Thus, with a spatial resolution only 1 order of magnitude worse than scanning tunneling microscopy measurements,2 atomic force microscopy (AFM) is seen to be a good choice in measurements on devices or other structures where measurement under ambient is desirable or tolerable. Historically, SPV has permitted the observation of a wide range of features in semiconducting samples, including mapping of dopant concentration, sodium accumulation, local charge, dislocations, precipitates, stacking faults, grain boundaries and microcracks, local resistivity, recombination time, band gap shifts (for instance in heterostructures), and stress.3 Experimental results will be presented which demonstrate the application of AFM/SPV to microcracking, dopant profiling and dislocation structure.