Epitaxial Growth of Novel II-VI Semiconductor Alloys for Ultraviolet Optical Devices

本研究的目的是建立一套适用于紫外光器件的新型II-VI族半导体合金的外延生长技术。研究结果如下：1. (Zn用气体源分子束外延（GS）技术在GaP衬底上生长了（S，Se）合金和ZnCdSSe-ZnSSe双异质结构（DH结构）。从DH结构的ZnCdSSe活性层观察到光致发光峰在3.2eV左右，这表明其能带结构为I型，载流子被限制在活性层中，这与能带排列计算一致。2.由于GSMBE中的生长速率很慢，因此研究了使用元素硫的MBE。3. RHEED观察表明，利用分子束外延技术在GaP（100）衬底上直接生长ZnS时，ZnS的生长模式为三维生长模式，在生长过程中出现了大量的孪晶 ...更多信息 保留。通过对生长条件的优化，发现在高温下生长的GaP衬底和ZnS缓冲层分别抑制了三维生长和孪晶的产生。4.通过氯掺杂，成功地实现了ZnS基合金的n型导电控制，最高可达2 × 10 ~<18><-3>（-3）cm ~ 3。在此基础上，通过ZnS缓冲层在取向差的GaP上制备了Au/ZnSSe/ZnCdSSe/ZnSSe：Cl MIS结构。与传统的MIS相比，本研究中的MIS的特征在于ZnCdSSe量子阱。该阱有望限制载流子并提高发射效率。首次在77 K下通过电流注入获得了400 nm的强紫外光发射，这些结果表明GaP体系上的（Zn，Cd）（S，Se）合金在紫外光器件方面具有很高的应用潜力。进一步研究晶体学质量的改善可能有助于实现光谱区的器件。少

The objective of this research is to establish epitaxial growth technique for novel II-VI semiconductor alloys which is to be applied to the optical devices in ultraviolet region. The results are summarized as follows.1. (Zn, Cd) (S,Se) alloys and a ZnCdSSe-ZnSSe double heterostructure (DH structure) were grown on GaP by gas-source (GS) molecular beam epitaxy (MBE). From the ZnCdSSe active layr of the DH structure photoluminescence peaking at around 3.2eV was observed, which suggests that the band structure was type-I and carriers were confined in the active layr in accordance with band-lineup calculation.2.Since the growth rate in GSMBE was quite slow, MBE using an elemental sulfur was investigated. To overcome the high vapor-pressure of an elemental sulfur, a cracking cell was designed, by which sufficient growth rate could be obtained.3.RHEED observation revealed that when ZnS was directly grown on a GaP (100) substrate by MBE,the growth mode was 3-dimensional and many twins were co … More ntained. It was found by optimization of growth conditions that 3-dimensional growth and twin generation were suppressed by a misoriented GaP substrate and a ZnS buffer layr grown at a high temperature, respectively.4.n-type conduction control in ZnS-based alloys was successfully achieved up to 2x10^<18>cm^<-3> by chlorine doping. However, p-type conduction was not obtained by nitrogen doping, unlike ZnSe-based alloys.5.On the basis of the above results, Au/ZnSSe/ZnCdSSe/ZnSSe : Cl MIS structure was fabricated on a misoriented GaP through ZnS buffer layr. Compared with conventional MIS,the MIS in this study is characterized by the ZnCdSSe quantum well. The well is expected to confine carriers and to enhance emission efficiency. Strong ultraviolet emission at 400nm was obtained by current injection at 77K for the first time.These results strongly suggest high potential of (Zn, Cd) (S,Se) alloys on GaP system for the application to ultraviolet optical devices. Further investigation for the improvement of crystallographic quality may contribute to the realization of devices in the spectral region. Less