Development of GaInP Solar Cells Grown by Hydride Vapor Phase Epitaxy

We demonstrate the growth of homojunction GaInP solar cells by dynamic hydride vapor phase epitaxy for the first time. Simple unpassivated n-on-p structures grown in an inverted configuration with gold back reflectors were analyzed. Short wavelength performance varied strongly with emitter thickness, since collection in the emitter was limited by the lack of surface passivation. Collection in the base increased strongly with decreasing doping density, in the range 1 × 10¹⁶ - 5 × 10¹⁷ cm^-3. Optical modeling indicated that, in our best device, doped ∼1 × 10¹⁶ cm^-3, almost 94% of photons that passed through the emitter were collected. Modeling also indicated that the majority of collection occurs in the depletion region with this design, suggesting that nonradiative recombination there might limit device performance. In agreement with this observation, the experimental dark J-V curve exhibited an ideality factor near n = 2. Thus, limitation of deep level carrier traps in the material is a path to improved performance. Preliminary experiments indicate that a reduced V/III ratio, which potentially affects the density of these presumed traps, improves cell performance. With reduced V/III ratio, we demonstrate a ∼13% efficient GaInP cell measured under the 1-sun AM1.5G spectrum. This cell had an antireflective coating, but no front surface passivation.