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Use of Ge Doping in Obtaining High Efficiency Ga(1-x)Al(x)As GaAs Solar Cells and Alternate Structures for Obtaining High Air Mass Zero Efficiencies

IP.com Disclosure Number: IPCOM000079664D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Hovel, HJ: AUTHOR [+2]

Abstract

In outer space (Air Mass zero), a considerable portion (15%) of the solar radiation lies in the ultraviolet, with photon energies greater than 2.7 eV. To obtain the highest efficiencies for outer space operation, the following arrangements extend the response of solar cells to higher energies.

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Use of Ge Doping in Obtaining High Efficiency Ga(1-x)Al(x)As GaAs Solar Cells and Alternate Structures for Obtaining High Air Mass Zero Efficiencies

In outer space (Air Mass zero), a considerable portion (15%) of the solar radiation lies in the ultraviolet, with photon energies greater than 2.7 eV. To obtain the highest efficiencies for outer space operation, the following arrangements extend the response of solar cells to higher energies.

The solar cells discussed hereinbelow are based on layered structures consisting of Ga(1-x)Al(x)As-GaAs, which respond to both low and high-energy photons and, therefore, increase the efficiency at Air Mass zero. In these structures, Ge should be used where possible as the p-type dopant. To maximize the efficiency of the solar cells, which are largely dominated by the diffusion lengths, advantage should be taken of the fact that electron diffusion lengths in Ge doped GaAs are several times higher than in Zn doped GaAs of the same doping level/I/.

In one arrangement shown in Fig. 1, an n-type GaAs substrate 1 has a p-type germanium doped GaAs layer 2 grown thereon. Layer 2 should be about 2 Mu thick and the doping level approximately 1-2 x 10/18/cm/-3/. Layer 2 may be grown, for example, by liquid phase epitaxy. In a subsequent step, a thin (< 1 Mu) layer 3 of p-type, Zn doped Ga(1-x)Al(x)As, where x > 0.7, is grown on the surface of layer 2 to eliminate surface recombination losses. Layer 3 can be made very thin because the Ge doped p-type GaAs region of layer 2 is thick enough and heavily doped enough to provide low-series resistance (where previously it was the Ga(1-x)Al(x)As that provided the low-series resistance). The diffusion lengths in layer at the Ge doping level indicated are 10 Mu or larger, so that a 2 Mu wide Ge doped Ga...