Ščajev Patrik, Mekys Algirdas, Subačius Liudvikas, Stanionytė Sandra, Kuciauskas Darius, Lynn Kelvin G, Swain Santosh K
Institute of Photonics and Nanotechnology, Faculty of Physics, Vilnius University, Saulėtekio Ave. 3, 10257, Vilnius, Lithuania.
Optoelectronics Department, Center for Physical Sciences and Technology, Saulėtekio Ave. 3, 10257, Vilnius, Lithuania.
Sci Rep. 2022 Jul 27;12(1):12851. doi: 10.1038/s41598-022-16994-7.
Cadmium telluride (CdTe) semiconductors are used in thin-film photovoltaics, detectors, and other optoelectronic applications. For all technologies, higher efficiency and sensitivity are achieved with reduced charge carrier recombination. In this study, we use state-of-the-art CdTe single crystals and electro-optical measurements to develop a detailed understanding of recombination rate dependence on excitation and temperature in CdTe. We study recombination and carrier dynamics in high-resistivity (undoped) and arsenic (As)-doped CdTe by employing absorption, the Hall effect, time-resolved photoluminescence, and pump-probe in the 80-600 K temperature range. We report extraordinarily long lifetimes (30 µs) at low temperatures in bulk undoped CdTe. Temperature dependencies of carrier density and mobility reveal ionization of the main acceptors and donors as well as dominant scattering by ionized impurities. We also distinguish different recombination defects. In particular, shallow As and deep V-As acceptors were responsible for p-type conductivity. AX donors were responsible for electron capture, while nonradiative recombination centers (V-As, As precipitates), and native defects (V-Te) were found to be dominant in p-type and n-type CdTe, respectively. Bimolecular and surface recombination rate temperature dependencies were also revealed, with bimolecular coefficient T temperature dependence and 170 meV effective surface barrier, leading to an increase in surface recombination velocity at high temperatures and excitations. The results of this study allowed us to conclude that enhanced crucible rotation growth of As-doped CdTe is advantageous to As activation, leading to longer lifetimes and larger mobilities and open-circuit voltages due to lower absorption and trapping.
碲化镉（CdTe）半导体用于薄膜光伏、探测器及其他光电子应用。对于所有技术而言，降低电荷载流子复合可实现更高的效率和灵敏度。在本研究中，我们使用最先进的CdTe单晶和电光测量方法，以深入了解CdTe中复合率对激发和温度的依赖性。我们通过在80 - 600 K温度范围内采用吸收、霍尔效应、时间分辨光致发光和泵浦探测技术，研究了高电阻率（未掺杂）和砷（As）掺杂的CdTe中的复合及载流子动力学。我们报告了块状未掺杂CdTe在低温下具有极长的寿命（30 μs）。载流子密度和迁移率的温度依赖性揭示了主要受主和施主的电离以及电离杂质的主导散射。我们还区分了不同的复合缺陷。特别是，浅As和深V - As受主导致了p型导电性。AX施主负责电子俘获，而在p型和n型CdTe中，非辐射复合中心（V - As、As沉淀）和本征缺陷（V - Te）分别占主导地位。还揭示了双分子和表面复合率的温度依赖性，双分子系数与温度有关，有效表面势垒为170 meV，导致高温和高激发下表面复合速度增加。本研究结果使我们得出结论，增强As掺杂CdTe的坩埚旋转生长有利于As的激活，由于较低的吸收和俘获，可导致更长的寿命、更大的迁移率和开路电压。
