A resonant cavity violet vertical cavity light emitting diode incorporating AlGaN DBR mirrors

Summary form only given. Advances in nitride-based blue and violet LEDs and lasers now suggest possibilities for more advanced geometries such as those based on vertical cavity structures. In our work, we have approached the design and fabrication of high-Q planar resonators by two methods. First, we have employed a lift-off method to separate the InGaN MQW heterostructure from its sapphire substrate so as to encase it within a high-Q cavity equipped by two dielectric DBRs. In this instance, first demonstrations of resonant cavity blue LEDs have been made. Secondly, we have revisited the very difficult problem of morphological quality of the in-situ grown AlGaN DBRs. Due to a small index contrast, these DBRs are generally plagued by defects such as cracks which form 'lateral cavities' and can lead to erroneous interpretation eg. of stimulated emission phenomena. In particular, by employing special strain engineering techniques, the nitride DBRs have recently improved to the point where such mirrors have been paired with dielectric DBRs for InGaN QW optical structures to achieve room temperature continuous-wave optically pumped near ultraviolet (380 nm). Here we show how an effective RCLED can be fabricated by incorporating an in-situ grown AlGaN/GaN DBR atop which the active InGaN MQW medium is grown, topped by a dielectric DBR.