K.J. Hong

Point defects in p-type CdIn2Te4 Bridgman grown crystals

Abstract Single crystal of p-CdIn 2 Te 4 was grown in a three-stage vertical electric furnace by using Bridgman method. The quality of the grown crystal has been investigated by X-ray diffraction and photoluminescence (PL) measurements. From the PL spectra of the as-grown CdIn 2 Te 4 crystal and the various heat-treated crystals, the (D 0 , X) emission was found to be the dominant intensity in the PL spectrum of the CdIn 2 Te 4 :Cd, while the (A 0 , X) emission completely disappeared in the CdIn 2 Te 4 :Cd. However, the (A 0 , X) emission in the PL spectrum of the CdIn 2 Te 4 :Te was the dominant intensity like in the as-grown CdIn 2 Te 4 crystal. These results indicated that the (D 0 , X) is associated with V Te which acted as donor and that the (A 0 , X) emission is related to V Cd which acted as acceptor, respectively. The p-CdIn 2 Te 4 crystal was obviously found to be converted into n-type after annealing in Cd atmosphere. The origin of (D 0 , A 0 ) emission and its TO phonon replicas is related to the interaction between donors such as V Te or Cd int , and acceptors such as V Cd or Te int . Also, the In in the CdIn 2 Te 4 was confirmed not to form the native defects because it existed in a stable bonding form.

The characterization of ZnSeGaAs epilayers grown by hot wall epitaxy

Abstract ZnSe GaAs , ZnSe : Zn GaAs , ZnSe : Zn GaAs (annealed in Zn vapor) and ZnSe GaAs (annealed in Se vapor) epilayers on (100) GaAs substrates have been grown by hot wall epitaxy under various growth conditions. X-ray double crystal rocking curves and photoluminescence measurements confirmed the good quality of the grown epilayers. The X-ray rocking curves show a FWHM value for the 0.37 μm thick ZnSe epilayer of 161 arcsec and a lattice mismatch between the (100) ZnSe epilayer and the (100) GaAs substrate of 0.27%. Photoluminescence studies indicate that the origin of the I 2 peak at 2.794 eV is associated with V Se at a neutral donor. It is also confirmed that the binding energy of the bound exciton (D 0 ,X), E b BX , is 14 meV and the binding energy E D , is 70 meV.

Growth of cadmium sulfide single crystal by the sublimation method

Abstract A cadmium sulfide (CdS) single crystal was grown by the sublimation method without a seed crystal in a two-stage vertical electric furnace. The temperature difference, 15°C, between the source and growth parts in the growth tube was in good agreement with the calculated value of 14.7°C. From the diffraction patterns, the single crystal exhibits a hexagonal structure and its c-axis is along the symmetry axis of the growth tube. The measured carrier concentration and mobility of the CdS single crystal are about 2.90 × 1016 cm−3 and 316 cm2/V·s, respectively, at room temperature. The energy bandgap obtained from photocurrent measurements follows Varshnis equation E g (T) = 2.552 eV − (5.75 × 10 −3 eV )T 2 (T + 3743) rather than a linear relationship E g (T) = 2.58 eV − (5.24 × 10 −4 eV K )T .

A Study on the Splitting of the Valance Band for a CdIn2te4 Single Crystal Using Photocurrent Measurement

The p‐CdIn2Te4 single crystal has been grown by using Bridgman method without a seed crystal in a three‐stage vertical electric furnace. From the photocurrent measurement, it was found that the three peaks of A, B, and C corresponded to the intrinsic transition due to the band‐to‐band transition from the valence band state Γ 7(A), Γ 6(B), and Γ 7(C) to the conduction band state Γ 6, respectively. Also, the valence band splitting of the CdIn2Te4 crystal has been first confirmed through the photocurrent spectroscopy. The crystal field splitting and the spin orbit splitting were obtained to be 0.2360 and 0.1119 eV, respectively. Also, the temperature dependence of the band gap energy of the CdIn2Te4 crystal has been driven as the following equation of Eg(T) = Eg(0) − (9.43 × 10−3)T2/(2676 + T). In this equation, the Eg(0) was estimated to be 1.4750, 1.7110, and 1.8229 eV at the valence band state A, B, and C, respectively. The band gap energy of the p‐CdIn2Te4 at room temperature was determined to be 1.2023 eV.

A Study on Annealing Effects of P‐CdIn2Te4 Single Crystal Obtained from Photoluminescence Measurement

The p‐CdIn2Te4 single crystal was grown in the three‐stage vertical electric furnace by using Bridgman method. The quality of the grown crystal has been investigated by the x‐ray diffraction and the photoluminescence measurements. From the photoluminescence spectra of the as‐grown CdIn2Te4 crystal and the various heat‐treated crystals, the (Do, X) emission was found to be the dominant intensity in the photoluminescence spectrum of the CdIn2Te4:Cd, while the (Ao, X) emission completely disappeared in the CdIn2Te4:Cd. However, the (Ao, X) emission in the photoluminescence spectrum of the CdIn2Te4:Te was the dominant intensity like an as‐grown CdIn2Te4 crystal. These results indicated that the (Do, X) is associated with VTe acted as donor and that the (Ao, X) emission is related to VCd acted as acceptor, respectively. The p‐CdIn2Te4 crystal was found to be obviously converted into the n‐type after annealing in the Cd atmosphere. The origin of (Do, Ao) emission and its TO phonon replicas is related to the int...

A Study on Properties of Infrared Detector for a HGCDTE Epilayers Using Photocurrent Measurement

Hg1−xCdxTe (MCT) was grown by hot wall epitaxy. Prior to the MCT growth, the CdTe (111) buffer layer was grown on the GaAs substrate at the temperature of 590 °C for 15 min. When the thickness of the CdTe buffer layer was 5 μm or thicker, the full width at half maximum values obtained from the x‐ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe (111) /GaAs substrate at various temperatures in situ. The crystal quality for those epilayers was investigated by means of the x‐ray rocking curves and the photocurrent experiment. The photoconductor characterization for the epilayers was also measured. The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were turned out.

A study on splitting of the valence band for a AgInS2/GaAs epilayer using photocurrent measurement

The chalcopyrite AgInS2 epilayers were grown on the GaAs substrate by using a hot-wall epitaxy (HWE) method. The temperature dependence of the energy band gap of the AgInS2 obtained from the absorption spectra was well described by the Varshni’s relation, Eg(T)=2.1365 eV-(9.89×10−3 eV)T2/(2930+T). In addition, we obtained the free exciton binding energy, 0.1115 eV, for the chalcopyrite AgInS2/GaAs by using Shay’s result. The crystal field and the spin-orbit splitting energies for the valence band of the AgInS2 have been estimated to be 0.1541 eV and 0.0129 eV, respectively, by means of the photocurrent spectra and the Hopfield quasicubic model. These results indicate that the splitting of the Δ so definitely exists in the Γ5 states of the valence band of the AgInS2/GaAs epilayer. The three photocurrent peaks observed at 10 K are ascribed to the A1, B1-, and C1-exciton peaks for n=1. Also, we obtained the A∞- and B∞-exciton peaks from the PC spectrum at 293 K. Therefore, we conclude that the peaks observed...

A study on annealing effects of AgInS2/GaAs epilayer obtained from photoluminescence measurements

The AgInS2 epilayers with a chalcopyrite structure grown using a hot-wall epitaxy (HWE) method have been confirmed to be a high quality crystal. From the optical absorption measurement, the temperature dependence of the energy band gap on AgInS2/GaAs was found to be Eg(T)=2.1365 eV−(9.89×10−3 eV)T2/(2930+T). After the as-grown AgInS2/GaAs was annealed in Ag-, S-, and In-atmospheres, the origin of point defects of AgInS2/GaAs has been investigated by using the photoluminescence (PL) at 10 K. The native defects of VAg, VS, Agint, and Sint obtained from PL measurements were classified as a donors or acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted AgInS2/GaAs to an optical p-type. Also, we confirmed that In in AgInS2/GaAs did not form the native defects because In in AgInS2 did exist in the form of stable bonds.