42% conversion efficiency in 1-cm2-area InGaAsP laser power converters

We formed InGaAsP laser power converters (LPCs) with a device area of 1 cm2 for a 1064 nm laser using metalorganic chemical vapor deposition. Au electroplating was adopted to form a 11-μm-thick Au surface electrode with a width of 23 μm and a shadowing loss of 7% to suppress the power loss by the series resistance (RS) at high intensity laser illumination. The fill factor (FF) increased with irradiated 1064 nm laser intensity and reached a maximum of 76.9% at 3 W cm−2 irradiation owing to a thick Au surface electrode. The J-V curves under laser illumination was fitted with a one-diode model and the RS was calculated to be 1.3 × 10–2 Ωcm2 at 5 W cm−2 laser irradiation. This value is approximately as half as that in the InGaAsP LPC with an area of 0.06 mm2 and a 3.4-μm-thick surface Au electrode reported in our previous study. The conversion efficiency (η) of 42.0% and the FF of 76.7% were achieved at 4.0 W cm−2 laser irradiation with a wavelength of 1064 nm. To our knowledge, this is the highest of all single-junction LPCs for a 1064 nm laser with a device area of 1 cm2 or larger reported so far. The temperature-induced degradation of η was calculated to be -0.22%rel. K−1 for the 1-cm2-area sample.