Preparation And Properties Of GaN Based LED And ZnO Nanowire

With the progress of science and technology, semiconductor lighting field has achieved great progress. As a kind of green energy, LED has penetrated into people’s lives. The GaN based blue LED technology and the potential application prospect of ZnO in blue LED has greatly promoted the development of the white LED.On the one hand, GaN is a direct band gap semiconductor, and the band gap is 3.4 eV. Otherwise, GaN has a high thermal conductivity, a stable chemical property, and a strong ability to resist radiation. These make GaN has widely applications in the fields of green and blue light-emitting devices and detectors. Scientists have focused on the improvement of the PL efficiency of GaN based LED for many years. At present, most scientists assume the internal quantum efficiency (IQE) at low temperature to be 100%. However, through the experiments, we found that the maximum value of the internal quantum efficiency of InGaN/GaN MQWs was not at the very low temperature. Therefore, it is necessary to further discuss and revise the measurement method of the quantum efficiency.On the other hand, ZnO also has excellent optical properties in semiconductor lighting field. Firstly, the band gap of ZnO is 3.37 eV at room temperature and the band-to-band emission is in the near ultraviolet region, its exciton binding energy is about 60 meV. The exciton binding energy of ZnO is 26 meV at room temperature, which makes ZnO exciton stable at room temperature and means that the exciton recombination can be achieved at room temperature. Compared to the electronic to hole recombination, the exciton recombination has a much larger emission efficiency, which makes ZnO has a very broad prospects in white solid lighting. Secondly, ZnO is easily crystallized and the production method of ZnO is very simple, at the same time, the growth temperature of ZnO is only 500 ℃. At present, ZnO has been widely used in solar cell, UV absorbing material and pressure sensitive resistance sensor. However, the growth of high quality and good stability P type ZnO nanostructures is still difficult for scientists.In this paper, a more accurate method for measuring the quantum efficiency of InGaN/GaN MQW structure is introduced in detail. At the same time, the preparation of one dimensional ZnO nanomaterials has been explored. The main conclusions of the dissertation are listed below.1. The method for measuring the internal quantum efficiency of InGaN/GaN MQW is as follows. First, measure the PL spectra of the samples under different temperatures and. Then make the dependence of PL efficiency on temperatures in different excitation powers or the dependence of PL efficiency on excitation powers in different temperatures and set the maximum PL efficiency to be IQE of 100%, thus the IQE at other temperatures and injected carrier densities are determined accordingly.2. In the preparation of ZnO nanomaterials, we have introduced some preparation work of ZnO nanowire arrays prepared by CVD method. Including the effect of the seed layer growing method, the influence of the distance between the substrate and the source and the influence of the seed layer thickness on the surface morphology of ZnO nanowires.