Processing Techniques for Dilute Nitride Gallium Arsenide Intermediate-Band Solar Cell Structures
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A solar cell processing procedure is calibrated for dilute nitride GaAs intermediate band solar cellstructures, and applied to a reference GaAs cell. The processing consists of front and backsidecontact metalization, a mesa etch, an etch through a heavily doped contact region, a SiNx antireective coating deposition, and a contact opening etch. The backside contact requires ananneal to become Ohmic. A poor turnout of the processed reference GaAs solar cell and timeconstraints prohibited processing of actual intermediate band solar cells. The efficiency of thereference cell was unacceptably low and major sources of loss are thought to be due to a highseries resistance as well as non-radiative recombination due to Al0.4Ga0.6As oxidation. Sourcesof series resistance may arise from poor conduction properties of the window and emitter layerof the reference cell, poor quality contacts, and residual SiNx on the contacts. Further measuresshould be taken to eliminate these problems before processing actual structures.