I-V And C-V Characteristics of nGaAs-nInSb Heterojunctions Obtained by Pulsed Laser Deposition Technique
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I-V And C-V Characteristics of nGaAs-nInSb Heterojunctions Obtained by Pulsed Laser Deposition Technique Karapet E. Avdjian Department of Semiconductor Electronics, Institute of Radiophysics & Electronics, National Ac. Sci. of Armenia, 1 Brs. Alikhanian st., Ashtarak, 378410, Armenia ABSTRACT Using pulsed laser deposition technique, nGaAs-nInSb heterojunctions (HJs) are obtained. Their electrical properties are studied. The Current-Voltage characteristics show that obtained HJs possess rectifying properties. The rectification coefficient depends strongly on the doping level of GaAs substrate. The linear dependence of C-2 (V) curve in Capacitance-Voltage characteristics, as well as the change of photo-response sign with wavelength, indicates that the HJs have abrupt interface, which is, to the best of our knowledge, a novel result for these HJ materials. The full number of interface states arising due to the lattice mismatch is determined which is in agreement with Hall measurements. Current-Voltage characteristics of obtained HJs are analogous to those of metal-semiconductor junction. Based on the obtained results the energy band diagrams of nGaAs-nInSb HJ is constructed taking into account the interface states.
INTRODUCTION Owing to its many advantages (such as technology flexibility, low temperature of crystalline growth, as well as production of thin and ultrathin layers of actually any material) the pulsed laser deposition (PLD) has its leading role in fabrication of thin semiconductor materials. In recent years, a growth of interest is observed in using the PLD for production of semiconductor heterojunctions (HJ). Due to a large lattice mismatch (~14%) the nInSb-nGaAs type HJs refer to the class of non ideal HJs. Earlier, E.D. Hinkley and R.H. Rediker [1] reported the fabrication of nGaAsnInSb HJs obtained by fusion of InSb into the GaAs. Nevertheless, there are no reports to our knowledge on the fabrication of crystalline nInSb-nGaAs HJs with abrupt interface using the usual techniques. This might be due to the difficulty of crystalline growth of HJ materials with large lattice mismatch. Only recently, in [2] the possibility of fabrication of crystalline nInSb-nGaAs HJs with abrupt interfaces was shown, and the results were used for analysis of an infrared (~5-6 µm) pyrometer. However, the electrical characteristics of these HJs were not presented in [2]. In the present work, crystalline nGaAs-nInSb HJs are fabricated based on the PLD technique, and their electrical properties are studied.
EXPERIMENT The facility for fabrication of nGaAs-nInSb HJs included a Q-switched laser on Nd3+ (pulse length is 30 nsec., energy per pulse is 1 J, intensity in the irradiation area of the target is ~108 W/sm2) and a vacuum chamber with residual pressure of ~10-6 Torr. Polished nGaAs slabs with various doping degrees (5⋅1016−5⋅1018 sm-3) were used as substrates, and nInSb pellets with doping degree 1014 sm-3 were used as target material. The nInSb layers
H9.25.1
with ~0.1µm thickness were deposited in vacuum of ~10-6 Tor
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