ZnTe single crystal growth by the liquid encapsulated pulling method

Abstract

Large diameter ZnTe single crystals were grown by the liquid-encapsulated pulling method using a double crucible. Crystals of around 80 mm in diameter and 40 mm in length were reproducibly obtained by this method. Both 〈100〉 and 〈110〉 crystals were successfully grown. The strong facet growth was observed when the shoulder part of the bulk was formed. Rectangular facet growth was observed in 〈100〉 growth and hexagonal facet growth was observed in 〈110〉 growth. The etch pit density of the grown crystal was lower than 10000 cm -2 and the strain in the crystal was lower than that of modified liquid encapsulated Kyropoulos method.1 Introduction ZnTe is a promising material for pure-green light emitting diodes (LEDs), green laser diodes (LDs) [1, 2] and electro-optic (EO) devices [3][4][5]. In order to develop these ZnTe based applications, large diameter single crystal substrates are necessary. It is, however, well known that growing II-VI semiconductor single crystals is very difficult owing to inferior physical properties [6]. The liquid encapsulated Czochralski (LEC) method has not been successfully applied to II-VI materials. We believe that the large temperature gradient of the LEC method [7] causes the difficulty of the single crystal growth owing to the the instability of the melt and generation of crystal defects. In our previous work, ZnTe single crystals were successfully obtained by modified liquid encapsulated Kyropoulos [8] (LEK) method using the small temperature gradient [9]. Our LEK crystals, however, had large strain and were sometimes cracked because of the difference in the thermal expansion coefficient between ZnTe and the encapsulant since the grown crystals were cooled in the encapsulant.In order to solve this problem, we tried to grow ZnTe single crystals by the liquid-encapsulated pulling method using a double crucible as the new growth method improved from the LEK and the LEC methods. In this paper, crystal growth of ZnTe by the double-crucible liquid-encapsulated pulling (DCP) method is reported.

Practical method to estimate the standard deviation in absorption coefficients measured with THz time-domain spectroscopy

“…The THz-TDS system used for the measurement is the Rayfact SpecTera [12] (Tochigi Nikon Corporation) consisting of a compact femto-second fiber laser (Femtolite, IMRA Inc.) with a pulse width of <100 fs and 20 mW average power and LTGaAs photoconductive antennas as THz emitter and detector. Three ZnTe crystals with different thickness (0.767, 1.496 and 2.976 mm) supplied commercially by Nippon Mining and Metals Co. Ltd. [13] are used as samples and they have very low absorption coefficient in the frequency range of 0.2-3 THz [14]. The time-domain data of 1024 points is taken in one scan of time delay line with the frequency resolution of 0.024 THz (0.814 cm À1 ), which needs about 10 min for each scan.…”

Accurate Complex Refractive Index with Standard Deviation of ZnTe Measured by Terahertz Time Domain Spectroscopy

“…During measurement, the sample is placed in the collimated beam and all the measurements were performed at room temperature and atmospheric pressure. ZnTe samples, which are grown by liquid encapsulated pulling method 22) and cut along the h110i surface, are acquired from JX Nippon Mining and Metals. Three ZnTe samples with different thickness are prepared from the same crystal.…”