Characterization of EL2 distribution on semi‐insulating GaAs wafer by optically assisted imperfection profile
An improved nondestructive characterization technique is
developed to measure the relative density distribution of the EL2 level in
undoped semi‐insulating (SI) GaAs wafers at
room temperature. Experimentally, the resistance of a small area of the wafer is
measured twice, first with greater than band‐gap illumination outside a small masked area and then with a
narrow‐band optical filter
centered at 1074 nm in place of the masked area. The difference of the two
measured resistances is shown to be proportional to the density of the EL2
level. By moving the masked area across the wafer while taking resistance
measurements, the relative density variation of EL2 can be determined. A
theoretical discussion based on the commonly used compensation model for
undoped SI GaAs materials is presented to interpret the experimental data.
A technique for applying electrical contacts to SI GaAs materials by
ultrasonic soldering has been developed to achieve reproducible measurements.
Although only GaAs materials were investigated, this optically
assisted imperfection profile can be applied to study other high‐resistivity semiconductors.
Source:IEEE
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