Physics of high-efficiency 240-260 nm deep-ultraviolet lasers and light-emitting diodes on AIGaN substrate

摘要

High-efficiency Ⅲ-nitride deep-ultraviolet (DUV) lasers and light-emitting diodes (LEDs) with emission wavelengths of 240-260 nm are extremely difficult to realize due to large defect density from Ill-nitride materials and existence of optical polarization crossover from conventional AlGaN-based quantum wells (QWs). Free-standing wurtzite AlGaN templates have been studied and developed recently; however, the physics and optical properties of AlGaN-based emitters on AIGaN templates are still relatively lacking. Therefore, this work theoretically investigates the optical properties and quantum efficiencies of the AlGaN-based QW on AIGaN substrates. The physics analysis based on a self-consistent 6-band k·p model shows the transverse electric (TE)-polarized optical gain increases from 558 cm~(-1) by using Al_(0.51)Ga_(0.49)N/AlN QW on the A1N substrate to 2875 cm~(-1) by using Al_(0.48)Ga_(0.52)N/Al_(0.72)Ga_(0.28)N QW on the Al_(0.72)Ga_(0.28)N substrate at 260 nm, which is attributed to the reduced strain effect and valence band rearrangement by using the AIGaN substrate. Correspondingly, the radiative recombination efficiency increases 1.66-4.43 times based on different Shockley-Read-Hall coefficients, indicating the promising potential of the use of the AlGaN substrate for high-efficiency DUV lasers and LEDs.