Growth of thick CdTe epilayers on GaAs substrates and evaluation of CdTe/n+-GaAs heterojunction diodes for an X-ray imaging detector
Growth of thick CdTe epilayers on GaAs substrates and evaluation of CdTe/n+-GaAs heterojunction diodes for an X-ray imaging detector
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DOI：
10.1007/s11664-004-0060-7
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发表时间：
2004-06
影响因子：
2.1
通讯作者：
M. Niraula;K. Yasuda;Y. Nakanishi;K. Uchida;T. Mabuchi;Y. Agata;K. Suzuki
中科院分区：
文献类型：
--
作者：
M. Niraula;K. Yasuda;Y. Nakanishi;K. Uchida;T. Mabuchi;Y. Agata;K. Suzuki
报道了金属有机气相外延 (MOVPE) 系统中 (100) GaAs 衬底上厚度高达 200 µm 的厚 (100) CdTe 外延层的生长特性，以及 CdTe/n+-GaAs 异质结二极管的制造，以用于低能 X 射线成像探测器中的可能应用。 X 射线双晶摇摆曲线 (DCRC) 分析显示，生长的外延层具有高结构质量，其中 (400) 衍射峰的半峰全宽 (FWHM) 值在 50 角秒到 70 角秒之间。 4.2-K 光致发光 (PL) 显示出高强度束缚激子发射和非常小的缺陷相关峰。所制作的异质结二极管具有良好的整流性能和较低的反向偏置电流。通过飞行时间 (TOF) 测量来检查二极管的 X 射线检测能力，观察到良好的偏压相关光响应，但无法推断出载流子传输特性。研究发现，CdTe 层具有大量的俘获态，这是由于从衬底扩散的与镉相关的空位和 Ga 杂质以及相关的缺陷复合体所致。
The growth characteristics of thick (100) CdTe epitaxial layers of a thickness up to 200 µm on a (100) GaAs substrate in a metal-organic vapor-phase epitaxy (MOVPE) system and fabrication of CdTe/n+-GaAs heterojunction diodes for their possible applications in low-energy x-ray imaging detectors are reported. The grown epilayers were of high structural quality as revealed from the x-ray double-crystal rocking curve (DCRC) analysis, where the full-width at half-maximum (FWHM) values of the (400) diffraction peaks was between 50 arcsec and 70 arcsec. The 4.2-K photoluminescence (PL) showed high-intensity bound-excitonic emission and very small defect-related peaks. The heterojunction diode fabricated had a good rectification property with a low value of reverse-bias current. The x-ray detection capability of the diode was examined by the time-of-flight (TOF) measurement, where good bias-dependent photoresponse was observed, but no carrier transport property could be deduced. It was found that the CdTe layer has a large number of trapping states as attributed to the cadmium-related vacancy and Ga-impurity, diffused from the substrate, related defect complexes.