The Preparation, Characterization And Properties Of Thin Films Of Gan And Gan-based Study

The subject investigated in this thesis is to attempt a method for thin film preparation by using the combination of pulsed laser plasma and electron cyclotron resonance (ECR) plasma, which is ECR plasma assisted pulsed laser deposition (ECR-PLD) and in situ doping via coablation of two targets with two pulsed laser beams. The method is used to synthesize GaN, GaN:Er, GaN:Pr thin films and SiC, AlN thin films as the candidates of buffers between Si substrates and GaN thin films.Pulsed laser deposition (PLD) is a technique using the properties of laser to ablate materials and the ablation plasma deposit on the substrates as the form of thin films, which has been successfully used for the preparation of many kinds of thin films. ECR microwave discharge can produce plasma with high density, high degree of ionization, and high purity at low working pressures. We developed a method for film synthesis named ECR-PLD by combining PLD with ECR microwave plasma. This method colligates the advantages of PLD and ECR plasma at low temperatures. As one of the most promising wide band gap III- V semiconducting materials, GaN has attracted much attention because of its potential applications in optoelectronic devices. GaN is also prospective materials for full-color displays, detectors as well as high-power and high temperature electronics and radiation-resistant devices due to their excellent optical, thermal, mechanical properties. In this work, the GaAs target was ablated by the focused laser beam in the ambience of ECR nitrogen plasma to deposit GaN thin films at low temperatures. By analyzing the samples' components and structure, such as HEIBS, XPS, FTIR, we demonstrated the feasibility of the presented method for GaN thin films preparation through thin films synthesis mentioned above.Rare earth (RE) ions have been received wide attention because of its prominent light emission properties for applications on optical emission and full color display devices. People mostly use the method of MBE and MOCVD to synthesize III-V nitrides doped with Rare earth ions implantation and in situ doping during thin film growth. But there still exist many disadvantages such as damage to the host and ununiformity of the dopant in the former as well as difficult to increase doping concentration in the latter. In this work, a novel method for compound thin film synthesis and in situ doping based on plasma assisted pulsed laser deposition by coablating two targets by two laser beams through the preparation of Er-doped GaN and Pr-doped GaN thin films was demonstrated. With the assistance of ECR nitrogen plasma, the ablation of a polycrystalline GaAs target resulted in the reactive deposition of host GaN film, while the ablation of a metallic RE (Er, Pr) target provided with RE atoms for doping in the growing GaN film.The growth of GaN is on silicon due to the advantages of this substrate, which is low cost, large scale availability, good thermal and electrical conductivities. However, there exist large lattice mismatch and difference in thermal expansion coefficients between GaN and silicon. Buffer layer is one of useful methods; we prepare SiC using coablation of two targets with two pulsed laser beams and AlN using ECR-PLD as the candidates of buffer materials. We select AlN as the buffer materials by analyzing the samples' properties.Post-annealing is an effective way to improve prepared thin films' structures and qualities. We do some work about it to analyze the effect of anneal toward GaN thin films.Through synthesis of these thin films above, with some assistant ways containing buffer layer and anneal, we demonstrated a purpose of laser and ECR plasma on material preparation in the thesis at one hand and studied the properties of GaN related thin films at the other hand.