Preparation And Optoelectronic Performance Of ZnO/GaAs Heterojunction

ZnO as a II-VI oxide semiconductor has a wide durect band gap (3.37eV) and a highexciton binding energy (60meV), so it can achieve lower threshold of the ultraviolet emission.In addition, the ZnO material with advantages of non-toxic, low cost, good thermal stabilityand high mechanical strength, these advantages make ZnO has wide application prospect inblue/UV LED, transparent conductive electrode, UV detector, film transistor andoptoelectronic devices. However, due to the intrinsic point defect from the compensationeffect, the high quality of p-ZnO materials have been hard to get, this is a serious impedimentto the development of ZnO based homogeneous junction devices. In recent years, someresearchers use the p-type semiconductor materials instead of p-ZnO to make differentstructure of p-n junction devices. GaAs as a important III-V compound semiconductormaterials, is the core of material to prepare red LEDs and near-infrared light electrical devices.Due to doping with mature technology, GaAs can alternative the p-ZnO to prepare then-ZnO/p-GaAs heterojunction light-emitting device. At present, n-ZnO/p-GaAsheterojunction is still a relatively new material system. The research on the material system isstill in material growth study phase, there are less reports for the device applications.In this paper, the main research results are as follows:1. N-ZnO nanofilms were deposited with different experimental conditions by pulse laserdeposition technology. X-ray diffraction and photoluminescence test system were used tostudying the substrate temperature, oxygen pressure and annealing temperature on theinfluence of ZnO thin films.Research shows that when the substrate temperature and oxygenpressure are400℃and10pa respectively, the ZnO thin film has best quality ofcrystallization;With the increase of annealing temperature, the crystallization of ZnO thin filmquality is downward trend after rising first, when the annealing temperature is600℃, theZnO thin film has the best quality.By photoluminescence test, researches show that thesubstrate temperature, oxygen pressure and annealing temperature can influence thephotoluminescence properties of ZnO thin films.In addition, we used hydrothermal method toprepare ZnO nanorods on the Al2O3(0001) substrate which has high c-axis orientation, andstudy the influence of ZnO seed layer to structure and luminescence properties of ZnO nanorods.2. According to the optimal growth parameters of the ZnO thin film and nanorods, usingPLD technology and hydrothermal method ZnO thin film and ZnO nanorods were grown onthe p-GaAs substrate, we constructed n-ZnO films/p-GaAs and n-ZnO nanorods/p-GaAsheterojunction devices respectively, and study the structure and photoelectric properties oftwo kinds of device. The room temperature (RT) photoluminescence spectrum of n-ZnOfilms/p-GaAs contains a near ultraviolet emission peak and a wide luminescence band invisible region, they are corresponding to the near-band-edge emission and defects relateddeep-level emission of ZnO respectively. Besides, the near infrared emission centered at thenear infrared region is attributed to the radiative recombination of Be acceptor from p-GaAs.For the photoluminescence spectrum n-ZnO nanorods/p-GaAs, there is no GaAsphotoluminescence peak, to analyzing the reason is that the thickness of the ZnO nanorods isbigger, hindered the photoluminescence of GaAs. SEM and XED test show that ZnO thinfilms have good c-axis orientation and high crystallinity. It is important to note that XRD andSEM test results of n-ZnO/p-GaAs illustrate that Ga3O2between ZnO layer and GaAs layerwas observed, analysis the reason for this is that GaAs was oxy-genated by oxygen taken inthe process of sample preparation,then it forms a interlayer between ZnO and GaAs. Inaddition to n-ZnO/p-GaAs in photoelectric detection test, we found that when under thereverse voltage of-2v the device has the highest respomsivity of10.17A/W and the peakdetection rate of2.06*1010cmHz1/2/W. And the device has a strong selective infrared lightnear to850nm (FWHM of about30nm).