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A semiconductor researcher whose work with Jerry M. Woodall improved gallium arsenide solar cells using a heterojunction. A surface layer reduced surface recombination while transmitting much of the useful incident light. Comparing the spectral response before and after removing that layer exposed how surface losses suppress charge collection, connecting device efficiency with a measurable microscopic loss mechanism.^[ref]

A researcher in semiconductor devices whose joint work with H. J. Hovel demonstrated heterojunction solar cells made from gallium arsenide and an aluminum-containing alloy. The additional layer admits useful light while reducing surface recombination and electrical resistance. Their 1972 experiment illustrates why an efficient solar cell depends on controlling what happens to generated carriers at a surface, as well as on absorbing incident light.^[ref]

From the illuminated side downward, the p-type gallium arsenide cap provides a low-resistance route to the front metal contact. It should remain beneath the contact grid but be removed from the optical aperture to reduce parasitic absorption. The wider-band gap p-type aluminium gallium arsenide window transmits much of the useful light and reduces front-surface recombination of carriers in the adjacent absorber. The optical-window and reduced-recombination rationale has a primary experimental basis in early heteroface devices.^[ref]

The p-type gallium arsenide emitter and n-type gallium arsenide base form the p-n junction. Absorbed photons generate electrons and electron holes; diffusion and the junction's electric field direct them toward the appropriate contacts. The n-type aluminium gallium arsenide back-surface-field layer provides a barrier to minority holes moving toward the substrate and reduces rear recombination. The n-type gallium arsenide substrate supports the epitaxial layers and conducts majority carriers to the rear contact.

The front metal must collect current with limited shading and the back metal provides the return contact. Interpreting the patterned hatched region as the optical antireflection coating, it reduces reflected light over the exposed window. Carrier selectivity, low recombination, low series resistance and low shading must work together; the equilibrium junction field alone is not a source of electrical energy.