MOCVD外延Hg_(1-x)Cd_xTe/Cd_(1-y)Zn_yTe薄膜的光致发光

Photoluminescence ofHg_(1-x)Cd_xTe/Cd_(1-y)Zn_yTe Epitaxial Films Grown by MOCVD

利用Raman显微镜系统对两块用MOCVD方法在Cd0 96Zn0 0 4 Te衬底上生长的Hg0 8Cd0 2 Te外延薄膜样品在光谱范围 5 0～ 5 0 0 0cm-1进行了测量 ,在其中的一块样品上首次发现了 1 4 3eV至 1 93eV范围内出现的具有周期结构的光致发光峰 ,该发光峰对应的能带中心位于Hg0 8Cd0 2 Te外延层导带底上方 1 73eV ,在另外一块外延薄膜样品中仅观察到四个Raman散射峰 ,没有周期结构的发光峰。为了分析上述光致发光的起因 ,对两块样品进行了X射线的双晶回摆曲线样品结构分析 ,得出样品在 1 4 3eV至 1 93eV范围的光致发光峰是由于改进MOCVD生长工艺提高了样品的结构质量所致 ,通过分析指出该光致发光峰是来源于Hg0 8Cd0 2 Te外延层中的阴性离子空位的共振能级。

The fundamental physical properties of Hg 1-xCd x Te make it an excellent candidate material for infrared photoelectric detectors. Recently, much attention has been paid to Hg 1-xCd x films grown by different epitaxial techniques on the substrate Cd 1-y Zn y Te due to the possibility of fabricating large area detectors as well as high precision focal plane array detectors. Investigations of the phonon vibration spectra for Hg 1-xCd x are necessary to understand the lattice dynamics and to obtain structure information about the material. In this paper, the micro-Raman spectra of two MOCVD Hg 1-xCd x/Cd 1-yZn yTe epitaxial film samples were measured at room temperature within the spectral range of 50cm -1 to 5 000cm -1. The quasi-periodically micro-photoluminescent structure in the range from 50cm -1 to 5 000cm -1 was observed for the first time in one sample. The micro-photoluminescence results show that there is an anion vacancy resonance level far up in the conduction band, about 1.73eV above the conduction band edge in Hg 1-xCd x/Cd 1-yZn yTe epitaxial film. In the micro-Raman spectrum of another sample four main Raman peaks at 125.3cm -1, 140.8cm -1, 164.8cm -1 and 265.2cm -1 were observed. The Raman peak of 125.3cm -1 belongs to HgTe-like TO 1 phonon vibrational mode, 140.8cm -1 belongs to HgTe-like LO 1 phonon vibrational mode, 164.8cm -1 occurs due to CdTe-like LO 1 phonon vibration, and 265.2cm -1 come from the two-phonon mode TO 1(HgTe-like)+LO 1(HgTe-like). At the same time, X-ray double-crystal rocking curves were also obtained in order to check the structure quality of two samples. Our results definitely show that the quasi-periodically micro-photoluminescent structure is mainly due to the improvement in quality of the Hg 1-xCd xTe epilayer. The experimental results also demonstrate that micro-photoluminescence technique in micro-Raman system seems to be a good convenient, simple, contactless method to characterize the perfection of Hg 1-xCd xTe epitaxial films.