Laser beam induced current imaging of reactive ion etching induced n-type doping in HgCdTe
The nondestructive optical characterization technique of laser beam induced current (LBIC) has been used to illustrate the effects of reactive ion etching (RIE) of mid-wavelength infrared n-type HgCdTe. RIE may be used as a method of n-p junction formation, as a means of forming n+ ohmic contacts to wider bandgap HgCdTe, or for mesa isolation etching of epilayers for HgCdTe detectors and emitters. Along with experimental measurements of the LBIC phenomena, this paper introduces the simulation of LBIC signals using a commercial semiconductor device modeling package. A number of LBIC maps are presented for different wafer processing conditions, with the results being explained using the simulation software. The experimental and calculated results bring to light a number of previously unreported characteristics associated with the LBIC phenomena, including the effect of junction depth, temperature, and grading of the junction region. In addition to the LBIC technique confirming the presence of an n+ region after RIE processing, it also provides information regarding the depth of the n+ region and lateral extent of the doping.