Optical wireless communications with InGaN multiple-quantum-well photodiodes grown with the prestrained superlattice interlayer for light detection

InGaN multiple-quantum-well photodiodes (InGaN MQW PDs) grown with an underlying superlattice (SL) are proposed for light detection in optical wireless communications. Experimentally, it was found that the presence of the prestrained SL interlayer with a reduced barrier width can help to relief the biaxial strain of the overlying In0.16Ga0.84N/GaN MQW. This gives rise to a stable emission spectrum and a reduced lifetime of carrier recombination or increased carrier escape from the InGaN wells in proposed InGaN PDs. The improved carrier transport in InGaN MQWs with a reduced polarization field is responsible for the improvement in PD's photoresponsivity provided their In0.16Ga0.84N/GaN MQW was fully depleted under -5 V bias. Further increasing the depletion width by reverse bias, an additional photocurrent from the prestrained SL interlayer leads to the best PD photoresponsivity despite their detectivity also degrading at such a high voltage level (V = -10 V). On the other hand, a 250 Mbit/s directed optical link with a bit error rate of 8.8 x 10(-8) is proven to be feasible by using the near-ultraviolet laser diode (LD) and the proposed InGaN PDs (better 3-dB cut-off frequency of 76.1 MHz achieved even under zero bias) as the optical transmitter and the receiver, respectively. Furthermore, the practical application of LD-based optical wireless communications with the SL containing InGaN PDs through real-time transmission of digital TV signals (data rate similar to 270 Mbit/s) is also demonstrated.