Study On Carrier Injection In Deep Ultravilet Light Emitting Devices

AlGaN-based wide bandgap semiconductor material has an adjustable energy bandgap from 3.4 to 6.1 e V,covering the ultraviolet waveband from 200 to 365 nm,which makes it an irreplaceable semiconductor material system for the preparation of deep-ultraviolet light-emitting diodes(DUV-LEDs).This article aims to improve the injection characteristics(reducing the leakage current and increasing the hole injection)of carriers by optimizing the structure of AlGaN-based DUV-LEDs.We carried out systematic research work and the main innovative results are listed below:(1)The effect of modulated-taper p-AlGaN layer structure on the performance of AlGaN-based deep UV LED has been studied.In order to facilitate the comparative analysis,the conventional single aluminum p-type AlGaN layer,the conventional tapered AlGaN layer,the asymmetric modulated-taper AlGaN layer and the symmetric modulated-taper AlGaN layer were designed,respectively.By using APSYS software simulation,the results show that the use of modulated-taper AlGaN layer structure in DUV-LED can significantly reduce the electron leakage and increase the hole injection efficiency,so as to improve the radiation recombination rate and the overall performance of the device.In particular,the taper AlGaN layer with symmetric modulation further improves the performance of the device by further enhancing the electronic confinement capability and reducing the efficiency droop.(2)Inserting wells in the step-like p-type AlGaN layer of AlGaN-based DUV-LEDs has been investigated.Comparing with the conventional AlGaN layer structure and the step-like AlGaN layer structure design of the device performance.The simulation results show that adopting inserted-wells step-like AlGaN layer structure for DUV-LEDs with peak emission wavelength of 280 nm can effectively increase electron confinement capability and hole injection,thereby enhancing the wave function overlap of electrons and holes in the quantum well and radiation recombination rate in MQWs,which exhibit excellent device performance.(3)The effect of the V-type last quantum barrier(LQB)structure on the luminescence properties of the device in AlGaN-based DUV-LEDs has been studied.In order to facilitate the comparative analysis,the conventional single aluminum LQB structure and the V-type LQB structure were designed,respectively.By using APSYS software simulation,the results show that,the V-shaped structure design of the LQB in the active region can effectively suppress the polarization effect existing in the conventional deep ultraviolet light emitting diode structure.Therefore,the quantum confinement Stark effect of the active region is reduced and more holes can enter the active region and recombine with electrons,thereby increasing the internal quantum efficiency and light output efficiency of the LED.