Growth of Germanium Crystals by Time-varying Temperature Profile, CVT Method Giovanni Attolini, Giovanna Trevisi, Patrizia Ferro IMEM-CNR Institute, Parco Area delle Scienze 37A, 43124 Parma (Italy) Germanium is a semiconductor material with an indirect bandgap at 0.66 eV, has a diamond cubic crystal structure; due to its good properties, high carrier mobility, high dielectric constant is interesting for the realization of many electronic devices [1]. Due to its crystallographic characteristics, germanium is used in the semiconductor technology to prepare epitaxial structures; in combination with III-V's compounds it can be used both as a substrate and as an active layer. Germanium bulk crystals can be grown from melt using Czochralski method [2], it is possible to obtain high quality ingots that can be sliced and processed intowafers for semiconductor technology. The vapour phase technique has been also used to growth germanium "bulk" crystals: the physical vapour transport (PVT) is not convenient to prepare large crystals because germanium vapour pressure is too low at the melting point. This drawback can be solved by using the chemical vapour transport (CVT) technique[3,4] Here we report on the germanium crystals preparation by chemical vapour transport (CVT), using three different procedure: the Stationary Temperature Profile (STP), the Linear Time-varying Temperature Profile (LTVTP) and the LTVTP [5] followed by the Oscillatory Temperature Profile (OTP) in the same run. With the optimization of the growth parameters we have obtained a progressive increase of the crystal sizes and a reduction of the crystalline nuclei during the primary nucleation. As a final result we achieved the growth of only one crystal using the Linear Time-varying Temperature Profile associated with Oscillatory Temperature Profile (LTVTP+OTP). The crystals morphology observed by Scanning Electron Microscopy (SEM) shows details of their shape typical of cubic structure. The structural properties were studied by X-ray diffraction, from which we obtained a clear indication that all samples were single crystalline with diamond cubic structure. [1] I. Yonenaga, Germanium crystals, in Single Crystals of Electronic Materials, Chap.9 Edited by: Roberto Fornari Elsevier 2019 [2] G. K. Teal, & J. B. Little,. Phys. Rev. 1950, 78, 647 [3] A.V. Sandulova , P.S. Bogoyavlenskii and M.I. Dronyuk, Preparation of germanium and silicon single crystals from the gaseous phase by the use of a second element, Soviet Physics - Doklady 1964, 8(11), 1112 [4] R. Heinemann and P. Schmidt, Crystal Growth by Chemical Vapor Transport: Process Screening by Complementary Modeling and Experiment, Cryst. Growth Des. 2020, 20( 9), 5986 [5] C. Paorici, L. Zanotti, M. Curti, Time-varyngTemperature Profile CVD Methods for Growing CuInS2 and CdIn2S4 Crystals, Crystal Research and Technology 1982, 17, 917-924
Growth of Germanium Crystals by Time-varying Temperature Profile, CVT Methods
Giovanni Attolini;Giovanna Trevisi;Patrizia Ferro
2021
Abstract
Growth of Germanium Crystals by Time-varying Temperature Profile, CVT Method Giovanni Attolini, Giovanna Trevisi, Patrizia Ferro IMEM-CNR Institute, Parco Area delle Scienze 37A, 43124 Parma (Italy) Germanium is a semiconductor material with an indirect bandgap at 0.66 eV, has a diamond cubic crystal structure; due to its good properties, high carrier mobility, high dielectric constant is interesting for the realization of many electronic devices [1]. Due to its crystallographic characteristics, germanium is used in the semiconductor technology to prepare epitaxial structures; in combination with III-V's compounds it can be used both as a substrate and as an active layer. Germanium bulk crystals can be grown from melt using Czochralski method [2], it is possible to obtain high quality ingots that can be sliced and processed intowafers for semiconductor technology. The vapour phase technique has been also used to growth germanium "bulk" crystals: the physical vapour transport (PVT) is not convenient to prepare large crystals because germanium vapour pressure is too low at the melting point. This drawback can be solved by using the chemical vapour transport (CVT) technique[3,4] Here we report on the germanium crystals preparation by chemical vapour transport (CVT), using three different procedure: the Stationary Temperature Profile (STP), the Linear Time-varying Temperature Profile (LTVTP) and the LTVTP [5] followed by the Oscillatory Temperature Profile (OTP) in the same run. With the optimization of the growth parameters we have obtained a progressive increase of the crystal sizes and a reduction of the crystalline nuclei during the primary nucleation. As a final result we achieved the growth of only one crystal using the Linear Time-varying Temperature Profile associated with Oscillatory Temperature Profile (LTVTP+OTP). The crystals morphology observed by Scanning Electron Microscopy (SEM) shows details of their shape typical of cubic structure. The structural properties were studied by X-ray diffraction, from which we obtained a clear indication that all samples were single crystalline with diamond cubic structure. [1] I. Yonenaga, Germanium crystals, in Single Crystals of Electronic Materials, Chap.9 Edited by: Roberto Fornari Elsevier 2019 [2] G. K. Teal, & J. B. Little,. Phys. Rev. 1950, 78, 647 [3] A.V. Sandulova , P.S. Bogoyavlenskii and M.I. Dronyuk, Preparation of germanium and silicon single crystals from the gaseous phase by the use of a second element, Soviet Physics - Doklady 1964, 8(11), 1112 [4] R. Heinemann and P. Schmidt, Crystal Growth by Chemical Vapor Transport: Process Screening by Complementary Modeling and Experiment, Cryst. Growth Des. 2020, 20( 9), 5986 [5] C. Paorici, L. Zanotti, M. Curti, Time-varyngTemperature Profile CVD Methods for Growing CuInS2 and CdIn2S4 Crystals, Crystal Research and Technology 1982, 17, 917-924I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
