Optoelectronic Properties And Applications Of Ⅲ-Nitride Quantum Well

GroupⅢ-nitride semiconductors AIN, GaN, InN and their ternary alloys AlGaN, InAIN, GaInN and quaternary alloy AlInGaN have greater developing potential and wider application prospect than any other semiconductors, because their band gaps cover a wide range from deep ultraviolet to medial infrared. With recent breakthroughs in material growth and device fabrication technologies,Ⅲ-nitride semiconductors have important application value in optoelectronic devices, especially for light-emitting devices, such as light-emitting diodes (LEDs) and laser diodes (LDs). CommercialⅢ-nitride light-emitting devices usually apply the quantum well (QW) structure, which makes them have more excellent performance. Then, the study on the optoelectronic characteristics and application ofⅢ-nitride QW structure has important practical significance. AlthoughⅢ-nitride QW light-emitting device have made great progress, but still there are many issues to be resolved. This thesis will focus on some of the problems in the study forⅢ-nitride QW light-emitting devices. The main results are listed as follows:1. First, the theoretical model based on the modified k·p method was established for the optoelectronic properties ofⅢ-nitride QW structure. The effects of strain, well-coupling, valence band-mixing and polarization effect were fully considered in the theoretical model. The optoelectronic properties of Ill-nitride QW structure can be obtained by solving self-consistently the conduction band and valence band effective mass equation and Poisson equation. The simulation program for above theoretical model based on the k-p method was established using finite difference method.2. The influence of polarization effect on the optoelectronic properties of the InGaN/GaN multiple quantum well (MQW) structures were systematically analyzed employing the theoretical model based on the k-p method. The polarization effects were compared for different InGaN/GaN MQW structure with different In content in well layers. And the optoelectronic properties of the InGaN/GaN MQW structures with different well width and barrier thickness were theoretically investigated using the theoretical model based on the k-p method. The polarization effect can enhance the influence of well width and barrier thickness on optoelectronic properties of InGaN/GaN MQW structures. In this thesis two methods were proposed to reduce the polarization effect on the properties of the InGaN MQW structures by choosing InGaN or polarization-matched InAlGaN as the barrier material. The dependence of emission spectra of the InGaN MQW structures on the well width and barrier thickness also decreases when InGaN or polarization-matched InAlGaN is selected as the barrier material.3. A new approach for the design of phosphor-free monolithic dichromatic and trichromatic white LED were proposed by employing InAlGaN irregular multiple quantum well (IMQW) structures. The IMQW structures composed two different type QWs emitting complementary wavelengths can realize dichromatic LED and the IMQW structures assembled by combining the blue, green, and red QWs together can realize the trichromatic white LED. The optoelectronic properties of the designed InAlGaN IMQWs were analyzed in details using the theoretical model based on the k·p method. Numerical results show that monolithic dichromatic and trichromatic white LED can be obtained using properly designed InAlGaN IMQW structures. Furthermore, under the influence of polarization effect the InGaN IMQW structures for dichromatic and trichromatic white LED were optimized in order to obtain near white light emissions.4. A detailed theoretical model for the quantum transport withinⅢ-nitride QW structures was presented based on Wigner function. The carrier density distribution and electrostatic potential can be determined from the self-consistent solution of Poisson equation and the quantum Liouville equation for the Wigner function. The simulation program for above theoretical model based on the Wigner function was established using finite difference method. The carrier transport properties of InGaN/GaN QW structures at different bias voltage were calculated. And the optical properties of InGaN/GaN QW structure considering quantum transport were simulated applying a detailed theory based on Wigner function and k·p method.