Praparetion And Investigation Of GaN/ZnO Based Heterojunction Emitting Device

Compouds including AlN,InN,GaN,AlGaAs and InGaAlAs are all commonly used to form GaN based Nitride material.We can achieve consistently adjustable band gap from 0.7eV to 6.2eV by changing the proportion of AlN,InN and GaN. So GaN based group III nitride materials have become the hot research subjects in optoelectronic metarial field. Recent years, people have finalized p type GaN material leading to the commercialization of GaN based blue LEDs. And GaN based blue LD devices GaN has also been attained successfully. But with some disadvantages, such as high threshold voltage,high growth temperature and lack of matched substrate material, the development of GaN has been restricted. ZnO is another type of directly wide-band gap semiconductor materail with band gap of 3.37eV and high excitonic energy of 60meV which make ZnO very suitable to be used to fabricate more efficiently LEDs or LDs. But it's not easy to realize p-type ZnO material which limits the fabrication of high quality ZnO p-n homojunctions. So people usually try to form heterojunction to realize U/V light-emitting of ZnO. ZnO and GaN have the similar wide-band gap,lattice constant and low lattice dismatch, so they have become a better choice for n-ZnO/p-GaN heterojunction fabrication.In this paper,we use MOCVD epitaxy growth method to fabricate heterojunctions with MQWs ans AlGaN electron blocking layer.We surpevised the growth through online observation of MOCVD facility. And we used Hall test,photoluminescence emissions(PL) test and electroluminescence (EL)emissions to observe optical and electrical characteristics.This paper includes two parts:First, we fabricated n-ZnO/(InGaN/GaN)MQWs/p-GaN heterojunctions. We analyzed the growth through online observation curve. We did photoluminescence emissions (PL) and got the PL wavelength. And then we achieved n-ZnO/(InGaN/GaN)MQWs/p-GaN heterojunction by MOCVD growth methods. The heterojunction shows a representitive I-V characteristics and we compared this with n-ZnO/p-GaN heterojunction's I-V characteristics.Electroluminescence emissions shows the peak wave lengthof n-ZnO/(InGaN/GaN)MQWs/p-GaN heterojunction is 588nm which is also proved by sample picture with light emitting color between green and yellow.And we also studied the EL under different injection current into n-ZnO/MQWs/p-GaN heterojunction.Second, with MOCVD growth method, we got n-ZnO/i-ZnO/AlGaN/p-GaN heterojunctions.We studied the PL spectrum of AlGaN/p-GaN heterojunctions which are formed under different temperatures and we found the ones fabricated at 600℃showing the best quality. So we fabricated n-ZnO/i-ZnO/AlGaN/p-GaN heterojunctions under this optimal temperature condition.This kind of heterojunctions also have a representitive characters. And the EL spectrum shows the peak wavelength of n-ZnO/i-ZnO/AlGaN/p-GaN heterojunction is 379nm which is ultroviolet light and the wave is sharp with a small HWF which means the device has less defects.