Search of "Betavoltaic" For Edward Burke of Spire Corporation dated Nov. 30, 1990. C. J. Keavney, V. E. Haven, S. M. Vernon "Emitter Structures in MOCVDINP Solar Cells' 21st IEEE PVSC May, 1990. "Neutron Damage in Indium Phosphide' May 4, 1990 Edward A. Burke. Y. Suzuki, Y. Fukada, Y. Nagashima "An Indium Phos phide Solid State Detector A Possible Low energy gamma and Neutrino Detector' Nucl. Inst, and Meth. In Phys. Res, A275 (1989) 142-148. Masafumi Yamaguchi and Koushi Ando "Mechanism for Radiation Resistance of InP Solar Cells' J. Appl. Phys, 63(11) Jun. 1, 1988, pp. 5555-5562. I. Weinberg, C. K. Swartz and R. E. Hart, Jr. “Progress In Indium Phosphide Solar Cell Research' Ninth Space Photovoltaic Research and Technology Conference Apr. 19-21, 1988 pp. 17-26. Pearsall, Goodbody, Oparaku, Dollery and Hill"Effect of Isotropic Proton Irradiation on the Performance of USOO5260621A

Search of “Betavoltaic' for Edward Burke of Spire Corporation dated Nov. 30, 1990. C. J. Keaveney, V. E. Haven, S. M. Vernon “Emitter Structures in MOCVDINP Solar Cells' 21st IEEE PVSC May, 1990. “Neutron Damage in Indium Phosphide' May 4, 1990 Edward A. Burke. Y. Suzuki, Y. Fukada, Y. Nagashima "An Indium Phos phide Solid State Detector A Possible Low energy gamma and Neutrino Detector' Nucl. Inst. and Meth. In Phys. Res. A275 (1989) 142-148. Masafumi Yamaguchi and Koushi Ando "Mechanism for Radiation Resistance of InP Solar Cells'0 J. Appl. Phys. 63(11) Jun. 1, 1988, pp. 5555-5562. I. Weinberg, C. K. Swartz and R. E. Hart, Jr. “Progress

We demonstrate the effectiveness of using wet chemical techniques for Si and Ge planar surfaces to form nanoporous layers, and grow stable passivating oxide layers on planar and porous surfaces, after the front grid metallization step. Our results show that this passivated chemical oxide layer: (i) can serve as an effective window/first layer AR coating, (ii) is chemically, thermally and UV stable, (iii) can simplify the structure of Si, Ge and III-V based space solar cells, thereby reducing cost, and (iv) has the potential of improving the BOL and especially the EOL efficiency of Si and III-V based space solar cells

We use a chemically grown, thermally and chemically stable oxide, not only for surface passivation but also as an integral part of a 3-layer antireflection (AR) coating for thermally diffused p+n InP solar cells, thus solving the dual problem of surface passivation and surface reflection reduction on these cells. A phosphorus-rich interfacial oxide, In(PO3)3, is grown at the surface of the p+ emitter using an etchant based on HNO3, o-H3PO4 and H2O2. This oxide has the unique properties of passivating the surface as well as serving as a fairly efficient antireflective layer. We show that it is possible to design a three-layer AR coating for a thermally diffused p+n InP solar cell using the In(PO3)3-grown oxide as the first layer and either ZnS, MgF2 or a new combination MgF2 as the second and third layers respectively, so as to yield an overall theoretical reflectance of less than 2%

Commonly used first layer antireflection (AR) coatings for InP solar cells, such as ZnS, Sb/sub 2/O/sub 3/, SiO/sub 2/ and SiO, deposited either by electron-beam or by resistive evaporation, destroy the stoichiometry of the emitter surface. Consequently, the surface recombination velocity (SRV) at the emitter surface is significantly increased, leading to a reduction in the values of solar cell performance parameters. This can be prevented by growing, after contacting, a thin native oxide layer on the emitter surface. Best results are obtained using a phosphorus-rich chemical oxide grown by chemical oxidation using a newly developed etchant (PNP) based on HNO/sub 3/, o-H/sub 3/PO/sub 4/ and H/sub 2/O/sub 2/. The chemical oxide grown on p/sup +/-InP emitters, using the PNP etchant, passivates the surface and can be used as a first layer AR coating.<>

We have succeeded in fabricating diffused junction p/sup +/n(Cd,S) InP solar cells with measured AM0, 25/spl deg/C open circuit voltage (V/sub oc/) of 890 mV, which, to the best of our knowledge, is higher than previously reported V/sub oc/ values for any InP homojunction solar cells. The experiment-based projected achievable maximum AM0, 25/spl deg/C efficiency of these cells, using LEC grown substrates, is 21.3%. The maximum AM0, 25/spl deg/C efficiency recorded to date on bare cells is, however, only 13.2% due entirely to nonoptimized front grid, antireflection (AR) coating and emitter thickness. This paper summarizes advances in the technology of fabrication of p/sup +/n InP diffused structures and solar cells, undertaken in an effort to increase the cell efficiency. Based on the high radiation resistance and the excellent post-irradiation annealing and recovery demonstrated in the early tests done to date, as well as the projected high efficiency and low-cost high-volume fabricability, these cells show a very good potential for space photovoltaic applications.

On bare p+n (Cd,S) InP diffused solar cells, the authors recorded AMO, 25°C Voc values exceeding 880 mV. In this work they present some of their most recent results showing much lower carrier removal rates in the emitter of p+n (Cd,S) diffused structures as compared to p+n (Zn,S) structures after irradiation with 1013 cm-2, 3 MeV protons. They also show the complete recovery of emitter carrier concentration profiles of p+n (Cd,S) structures after about 2 months in the dark at room temperature, a behavior not observed for p+n (Zn,S) structures. The drop in ISC, FF and efficiency of diffused p+n (Cd,S) InP cells after proton irradiation is lower than previously reported values for n+p (Si,Zn) InP cells fabricated by MOCVD or n+p (S,Zn) InP cells fabricated by diffusion

By drastically reducing the defect densities of p/sup +/n (Cd,S) InP diffused structures the authors have succeeded in fabricating p/sup +/n InP solar cells with measured AM0, 25/spl deg/C V/sub /spl prop// values exceeding 880 mV, without anti-reflection (AR) coating. Experiment-based projected maximum achievable AM0, 25/spl deg/C efficiency of these cells is 21.3%. Preliminary investigation of the performance parameters of p/sup +/n (Cd,S) InP structures and solar cells after irradiation with 10/sup 13/ cm/sup -2/ 3MeV protons indicate higher radiation tolerance of this configuration as compared to n/sup +/p InP configuration due to its better annealing properties.<>

On bare p/sup +/n (Cd,S) InP diffused solar cells, the authors recorded AMO, 25/spl deg/C V/sub oc/ values exceeding 880 mV. In this work they present some of their most recent results showing much lower carrier removal rates in the emitter of p/sup +/n (Cd,S) diffused structures as compared to p/sup +/n (Zn,S) structures after irradiation with 10/sup 13/ cm/sup -2/, 3 MeV protons. They also show the complete recovery of emitter carrier concentration profiles of p/sup +/n (Cd,S) structures after about 2 months in the dark at room temperature, a behavior not observed for p/sup +/n (Zn,S) structures. The drop in I/sub SC/, FF and efficiency of diffused p/sup +/n (Cd,S) InP cells after proton irradiation is lower than previously reported values for n/sup +/p (Si,Zn) InP cells fabricated by MOCVD or n/sup +/p (S,Zn) InP cells fabricated by diffusion.< >

In order to optimize the fabrication of n+-p InP solar cells made by closed-ampoule diffusion of sulfur into p-InP:Cd substrates, we have investigated the influence of diffusion conditions on sulfur diffusion profiles. We show that S diffusion in InP is dominated by the P vacancy mechanism and is not characterized by a complementary error function as expected for an infinite source diffusion. The S diffusion mechanism in p-InP is qualitatively explained by examining the depth profiles of S, P, and In in the emitter layer and by taking into account the presence and composition of different compounds found to form in the In-P-S-O-Cd system as a result of diffusion.

The performance results of our most recently thermally diffused InP solar cells using the p(+)n (Cd,S) structures are presented. We have succeeded in fabricating cells with measured AMO, 25 C V(sub oc) exceeding 880 mV (bare cells) which to the best of our knowledge is higher than previously reported V(sub oc) values for any InP homojunction solar cells. The cells were fabricated by thinning the emitter, after Au-Zn front contacting, from its initial thickness of about 4.5 microns to about 0.6 microns. After thinning, the exposed surface of the emitter was passivated by a thin (approximately 50A) P-rich oxide. Based on the measured EQY and J(sub sc)-V(sub oc) characteristics of our experimental high V(sub oc) p(+)n InP solar cells, we project that reducing the emitter thickness to 0.3 microns, using an optimized AR coating, maintaining the surface hole concentration of 3 x 10(exp 18)cm(sup -3), reducing the grid shadowing from actual 10.55 percent to 6 percent and reducing the contact resistance will increase the actual measured 12.57 percent AMO 25 C efficiency to about 20.1 percent. By using our state-of-the-art p(+)n structures which have a surface hole concentration of 4 x 10(exp 18)cm(sup -3) and slightly improving the front surface passivation, an even higher practically achievable AMO, 25 C efficiency of 21.3 percent is projected.

A significant reduction of defect densities of n/sup +/p and p/sup +/n InP structures fabricated by closed-ampoule thermal diffusion was obtained after optimizing the diffusion process. For n/sup +/p structures, the lowest etch pit density (EPD) of 6*10/sup 5/ cm/sup -2/ was achieved after S diffusion into InP:Cd (N/sub A/=1.2*10/sup 16/ cm/sup -3/) substrates using a thin In(PO/sub 3/)/sub 3/-rich anodic oxide diffusion cap layer at a diffusion temperature of 660 degrees C, while the lowest EPD after S diffusion into InP:Zn (N/sub A/ approximately 2*10/sup 16/ cm/sup -3/) under similar diffusion conditions was 8*10/sup 6/ cm/sup -2/. For p/sup +/n structures, surface EPD values as low as 4*10/sup 2/ cm/sup -2/ were achieved in the case of Cd diffusion into InP:S (N/sub D/=3.5*10/sup 16/ cm/sup -3/) substrates at a diffusion temperature of 560 degrees C using a thin In(PO/sub 3/)/sub 3/-rich chemical oxide diffusion cap layer, while the lowest EPD in the case of Zn diffusion was 3*10/sup 5/ cm/sup -2/. The differences are explained by the large number of In/sub 2/S/sub 3/, InS, and Zn/sub 3/P/sub 2/ surface and deep precipitates detected in the case of n/sup +/-p(S, Zn) and p/sup +/-n (Zn, S)InP structures.<>

The possibility of fabricating thermally diffused p/sup +/n InP solar-cells with high open-circuit voltage without sacrificing the short circuit current is discussed. The p/sup +/n InP junctions were formed by Cd and Zn diffusion through a 3-5 nm thick anodic or chemical phosphorus-rich oxide cap layer grown on n:InP:S (with N/sub D/-N/sub A/=3.5*10/sup 16/ and 4.5*10/sup 17/ cm/sup -3/) Czochralski LEC-grown substrates. After thinning the emitter from its initial thickness of 1 to 2.5 mu m down to 0.06-0.15 mu m, the maximum efficiency was found when the emitter was 0.2 to 0.3 mu m thick. Typical AM0, 25 degrees C values of 854-860 mV were achieved for V/sub oc/, J/sub sc/ values were from 25.9 to 29.1 mA/cm/sup 2/ using only the P-rich passivating layer left after the thinning process as an antireflection coating.<>

Cd diffusion and Zn diffusion into n-InP:S (N/sub D/ =3.5*10/sup 16/ and 4.5*10/sup 17/ cm/sup -3/) were performed by a closed ampoule technique at diffusion temperatures from 500 to 600 degrees C by using either high-purity Cd and Zn or Cd/sub 3/P/sub 2/ and Zn/sub 3/P/sub 2/. The Czochralski LEC grown substrates with etch pit densities (EPDs) from 3*10/sup 4/ to 7*10/sup 4/ cm/sup -2/ were used. Diffusions were performed through either bare surfaces or using SiO/sub 2/ (50-100 AA thick) and phosphorus-rich anodic and chemical oxides (25-50 AA thick) as cap layers. Specular surfaces have been obtained after Cd diffusion from Cd/sub 3/P/sub 2/ through P-rich oxide cap layers with a very low surface dislocation density which goes through a minimum of 400-800 cm/sup -2/ at the diffusion temperature of 560 degrees C. AM0 250 degrees C V/sub oc/ values as high as 860 mV from solar cells made on these structures are reported.< >