Electrical and optical characterisation of low temperature grown InGaAs for photodiode applications

Dilute bismide and nitride alloys are promising semiconductors for bandgap engineering, opening additional design freedom for devices such as infrared photodiodes. Low growth temperatures are required to incorporate bismuth or nitrogen into III-V semiconductors. However, the effects of low growth temperature on dark current and responsivity are not well understood. In this work, a set of InGaAs p-i-n wafers were grown at a constant temperature of 250, 300, 400 and 500 degrees C for all p, i and n layers. A second set of wafers was grown where the p and n layers were grown at 500 degrees C while the i-layers were grown at 250, 300 and 400 degrees C. Photodiodes were fabricated from all seven wafers. When constant growth temperature was employed (for all p, i and n layers), we observed that photodiodes grown at 500 degrees C show dark current density at -1 V that is six orders of magnitude lower while the responsivity at an illumination wavelength of 1520 nm is 4.5 times higher than those from photodiodes grown at 250 degrees C. Results from the second set of wafers suggest that performance degradation can be recovered by growing the p and n layers at high temperature. For instance, comparing photodiodes with i-layers grown at 250 degrees C, photodiodes showed dark current density at -1 V that is five orders of magnitude lower when the p and n layers were grown at 500 degrees C. Postgrowth annealing, at 595 degrees C for 15 min, on the two wafers grown at 250 and 300 degrees C showed recovery of diode responsivity but no significant improvement in the dark current. Our work suggests that growth of the cap layer at high temperature is necessary to maintain the responsivity and minimise the dark current degradation, offering a pathway to developing novel photodiode materials that necessitate low growth temperatures. The data reported in this paper is available from the ORDA digital repository.