Crystal growth and structure, electrical, and optical characterization of the semiconductor Cu2SnSe3

Abstract

X-ray powder diffraction by p-type Cu2SnSe3, prepared by the vertical Bridgman–Stockbarger technique, shows that this material crystallizes in a monoclinic structure, space group Cc, with unit cell parameters a=6.5936(1) Å, b=12.1593(4) Å, c=6.6084(3) Å, and β=108.56(2)°. The temperature variation of the hole concentration p obtained from the Hall effect and electrical resistivity measurements from about 160 to 300 K, is explained as due to the thermal activation of an acceptor level with an ionization energy of 0.067 eV, whereas below 100 K, the conduction in the impurity band dominates the electrical transport process. From the analysis of the p vs T data, the density-of-states effective mass of the holes is estimated to be nearly of the same magnitude as the free electron mass. In the valence band, the temperature variation of the hole mobility is analyzed by taking into account the scattering of charge carriers by ionized and neutral impurities, and acoustic phonons. In the impurity band, the mobility is explained as due to the thermally activated hopping transport. From the analysis of the optical absorption spectra at room temperature, the fundamental energy gap was determined to be 0.843 eV. The photoconductivity spectra show the presence of a narrow band gap whose main peak is observed at 0.771 eV. This band is attributed to a free-to-bound transition from the defect acceptor level to the conduction band. The origin of this acceptor state, consistent with the chemical composition of the samples and screening effects, is tentatively attributed to selenium interstitials.

Structural diversity and electronic properties of Cu2SnX3(X=S, Se): A fir

“…Comparing with the experimental value 0.84 eV in Ref. 19,20, the calculated band gap is much smaller. This disagreement between calculations and experiments have also existed in CZTSe systems before, where earlier absorption spectrum measurement reported band gap sizes around 1.5 eV, much larger than our calculated value of 1.0 eV.…”

Electrical Properties of the Ordered Defect Compound CuIn3Se5

“…2 that the carrier concentration decreases with decreasing temperature and then starts to increase after going through a minimum. It is well known [21][22][23] that the carrier concentration in the conduction (valence) band increases whereas in the impurity band decreases with the increase of temperature. Furthermore, at a given temperature the total charge carrier concentration is the sum of those in the conduction (valence) and impurity bands at that temperature.…”

“…These are given in Refs. [20][21][22] and will not be repeated here. In the fit, the static dielectric constant e 0 optical e a the deformation potential E ac of the conduction (n-type), valence (p-type) bands, H, and m 0 were considered as adjustable parameters.…”

A wide-band-gap p-type thermoelectric material based on quaternary chalcogenides of Cu2ZnSnQ4 (Q=S,Se)

“…Recently, we proposed to meet this challenge by constructing materials with two structural/functional units, one electrically conducting and the other insulating, one example being Cu-doped chalcopyrite-type CuAlS 2 that has a wide band gap ͑about 3.4 eV͒ and a high . [9][10][11][12] Note that chalcopyrites, having a diamondlike tetrahedral framework structure, already include some low-phonon-conductive materials, such as Cu 2 SnS 3 and Cu 2 SnSe 3 , [13][14][15][16][17] which are used for infrared transmission. Therefore, it would be interesting to investigate whether the low phonon conduction can survive -enhancing doping in these large band-gap p-type semiconductors, thereby providing alternative TE materials.…”