A. Catalano

Polycrystalline Zn3P2 Schottky barrier solar cells

Energy conversion efficiencies as high as 5.96% are reported on polycrystalline transparent magnesium Zn3P2 diodes, 0.7 cm2 in area, tested under simulated AM1 illumination. The transparent Mg films with low sheet resistivities are obtained by dc sputtering. The effective minority‐carrier diffusion length in Zn3P2 is estimated from spectral response measurements and correlates well with the measured short‐circuit current. Loss analysis of the present cells shows a practical upper limit of 9% in conversion efficiency.

Zinc phosphide‐zinc oxide heterojunction solar cells

The photovoltaic properties of p‐Zn3P2/n‐ZnO heterojunction solar cells prepared by sputter deposition of ZnO on Zn3P2 substrates are reported. An active‐area power conversion efficiency of ∼2% has been obtained. The experimental results are discussed on the basis of an interface recombination model. The interface plays a significant role in determining the performance of the device.

Spectral response measurements of minority‐carrier diffusion length in Zn3P2

Spectral response measurements have been made on metal‐semiconductor junction diodes of single‐crystal p‐type zinc phosphide (Zn3P2) and Al, Mg, and Be. Two different experimental configurations were used and the minority‐carrier diffusion lengths calculated using a simple theoretical treatment of the data. In one experimental mode, the light is incident on the surface of the semiconductor opposite the metal junction. The spectral response is peaked and a lower limit on the diffusion length can be calculated from the peak height and sample thickness without detailed knowledge of the optical properties of the semiconductor. In the other mode, light is incident through the metal layer and the diffusion length is calculated by analyzing the spectral response function using known values of the optical absorption coefficient. On samples for which both modes were used, the results are in good agreement. The diffusion lengths measured are in the range of 5–10 μm.

Barrier heights of evaporated metal contacts on Zn3P2

Contact barrier heights are reported for twelve metals on zinc phosphide (Zn3P2). The results do not show a simple dependence on metal work function, but correlate with a chemical heat of reaction indicating the importance of chemical bonding at the metal/semiconductor interface.

Evidence of p/n homojunction formation in Zn3P2

Heating of magnesium/p‐Zn3P2 contacts at 100 °C results in a ∼ 102 lower reverse saturation current than found for the unheated metal‐semiconductor diode. Spectral response and electron‐beam‐induced current (EBIC) measurements show the formation of a buried junction upon heating, and the latter method has been used to obtain values of junction depth and minority carrier diffusion length. A model expressing the collection efficiency of an n‐on‐p homojunction shows good agreement with experiment when the minority carrier diffusion lengths and junction depth determined by EBIC measurements are used. This is the first evidence that p/n homojunctions may be formed in Zn3P2.