Photoluminescence and Photocurrent from InGaN/GaN Diodes with Quantum Wells of Different Widths and Polarities

We compare the optical properties of four pin diode samples differing by built-in field direction and width of the In0.17Ga0.83N quantum well in the active layer: two diodes with standard nip layer sequences and 2.6 and 15 nm well widths and two diodes with inverted pin layer ordering (due to the tunnel junction grown before the pin structure) also with 2.6 and 15 nm widths. We study photoluminescence and photocurrent in those samples (as a function of excitation power and applied voltage), revealing very different properties due to the interplay of built-in fields and screening by injected carriers. Out of the four types of diodes, the highest photocurrent efficiency was obtained (at reverse voltage) for the wide-well, inverted polarity diode. This diode also showed the highest PL intensity (at positive voltages) of our four samples. Diodes with wide wells have stable emission wavelengths (almost independent of bias and excitation power).