A Magneto‐Reflectivity Study of CuGaSe₂ Single Crystals

Abstract

CuGaSe2 single crystals are studied using magneto‐reflectivity at 4.2 K in magnetic fields B up to 20 T. The A and B free excitons, observed in the optical reflectivity spectra, blue shift with increasing B. A low‐field perturbation approach within the anisotropic hydrogenic model is used to fit the dependence of the spectral position of these excitons on B. The A and B exciton reduced masses of 0.115 m0 and 0.108 m0 (m0 is the free electron mass), Rydbergs of 12.9 and 12.2 meV, Bohr radii 5.08 and 5.4 nm, and effective hole masses of 0.64m0 and 0.48 m0, respectively, are determined.

The g-factor of CuGaSe2 studied by circularly polarised magneto-reflectance

“…The determined value of s d is very close to that of 9.82 µeV T −2 , determined for the A exciton in MPL measurements [9], and to 9.85 µeV T −2 , determined for the same exciton in MR experiments [15]. The difference can be attributed to variations in the orientation of the examined crystals.…”

“…According to the pseudo-binary diagram, reported in [18] the solidification of CuGaSe 2 , is peritectic. However high quality single crystals can be grown from the melt of a near stoichiometric mix of high purity Cu, Ga, and Se at slow cooling rates [14,15,19]. An x-ray powder diffraction pattern measured for the grown crystals, presented in figure 1, shows chalcopyrite structure reflexes of CuGaSe 2 and does not exhibit any significant signs of secondary phases in the material.…”

“…Measurements of the diamagnetic shifts and paramagnetic splitting were reported for the A and B free excitonic lines in magneto-photoluminescence (MPL) spectra of CuInSe 2 enabling the determination of the rate of diamagnetic shifts and g-factors in this material [13]. MPL and magneto-reflectance (MR) helped to determine the rate of diamagnetic shifts of the A [14] and B [15] free excitons, respectively, in the optical spectra of high structural quality single crystals of CuGaSe 2 . However, the application of magn etic fields did not result in a splitting of the free exciton features in such spectra suggesting that g-factors in CuGaSe 2 are much smaller than the spectral width of the A and B exciton lines.…”