Temperature‐Dependent Charge Carrier Diffusion in [0001¯] Direction of GaN Determined by Luminescence Evaluation of Buried InGaN Quantum Wells. Issue 6 (2nd April 2020) - Netzel, Carsten
Abstract : Temperature‐dependent transport of photoexcited charge carriers through a nominally undoped, c‐plane GaN layer toward buried InGaN quantum wells is investigated by continuous‐wave and time‐resolved photoluminescence spectroscopy. The excitation of the buried InGaN quantum wells is dominated by charge carrier diffusion through the GaN layer; photon recycling contributes only slightly. With temperature decreasing from 310 to 10 K, the diffusion length in [ 000 1 ¯ ] direction increases from 250 to 600 nm in the GaN layer. The diffusion length at 300 K also increases from 100 to 300 nm when increasing the excitation power density from 20 to 500 W cm −2 . The diffusion constant decreases from the low‐temperature value of ∼7 to 1.5 cm 2 s −1 at 310 K. The temperature dependence of the diffusion constant indicates that the diffusivity at room temperature is limited by optical phonon scattering. Consequently, higher diffusion constants in GaN‐based devices require a reduced operation temperature. To increase diffusion lengths at a fixed temperature, the effective recombination time has to be prolonged by reducing the number of nonradiative recombination centers. Abstract : Temperature‐dependent charge carrier diffusion in optically excited GaN/InGaN heterostructures is investigated. Diffusion lengths and diffusion constants are higher at cryogenic temperatures and decrease around room temperature because of optical phonon scattering. The diffusion process of charge carriers through a GaN layer is visualized by time‐resolved photoluminescence intensity from buried InGaN quantum wells (QWs).