Investigation of the hydrostatic pressure dependence of the E₀gap, the excitonic binding energy and the refractive index of MOCVD-grown ZnTe layers

Abstract

We have determined the pressure dependence of the excitonic transition energy in lhin MOVPE ZnTe layers by measuring the absorption coefficient and the retractive index. Pressures up to 12GPa were applied in a diamond anvil cell. A special gasket technique was used to s u p p m the scattered light. The absorption coefficient was measured in l p m thick films at T = 115K and at T = 300K up to SOOOOcm-'.The spectra are dominated by a sharp excitonic slmcture. Its pressure dependence is evaluated using a model which allowed us to determine the rate of pressure-induced shift of the binding energy d E , / d P and the rate of change of lhe Rydterg energy dR:/dP. The refractive index n was measured on 2.4pm-thick films at T = 300K and a t T = 115K by observing the pressure shift of lhe interference extrema in the transparency region. The resulting refractive index was extrapolated to the frequency of the longitudinal optical phonon to obtain the constant 6 -. The Static dielectric constant 6,< was obtained using the LyddaneSachs-'Eller relation. Using this value and the determined effective masses at the applied pressures, we calculated the exciton binding energy. At the pressure P = 9.4GPa. a phase transition was observed. The obtained spectra far this phase were compared with a model describing indirect transitions in semiconductors. A further phase transition was observed at P = I0.9GPa.

Structural, mechanical and electronic properties of ZnTe polymorphs under pressure

“…As shown in Table 5, the exchange correlation potential described by Engel-Vosko formalism within GGA (EV-GGA) used by Nourbakhsh [18], Gupta et al [17] and Charifi et al [43] is yielding better results for the direct bandgap at point for B3 structure. On the other hand, our results for the linear and quadratic pressure coefficients of the direct bandgap are more compatible with the experimental values [41,44] than the previous works using LDA [20,21] and EV-GGA [18]. The indirect bandgaps along the symmetry directions of → X and → L and their pressure derivatives calculated for B3 structure are compared with the previous calculations using LDA and available experiments [41,44] in Table 5.…”

“…The results for both structures are presented in Table 5. It is clearly seen that our results and the previous calculations by different methods for energy band gap are underestimated in comparison with the experimental values of 2.38 eV [41] and 2.26 eV [42]. It is well known that the LDA or GGA within DFT does not sufficiently describe the eigenvalues of the electronic states, hence yielding quantitative underestimations of band-gaps [20,43].…”

“…The indirect bandgaps along the symmetry directions of → X and → L and their pressure derivatives calculated for B3 structure are compared with the previous calculations using LDA and available experiments [41,44] in Table 5. They are in good agreement with the other calculations Table 5 The energy band gap Eg(eV) and the linear ˛(× 10 −2 eV GPa −1 ) and quadratic pressure coefficients ˇ(× 10 −3 eV GPa −2 ) of ZnTe in the B3, B9 and B33 structures along different transitions, compared with available experiments [41,42] and previous theoretical calculations [15,17,18,20,21,43]. [20,21].…”

Structural, electronic, linear, and nonlinear optical properties of ZnCdTe2 chalcopyrite

“…This value is lower than the experimental value (1.99 eV) [25] and not far from the value of 0.71 eV obtained by same authors, using LDA-LAPW method. We worth noting that the above experimental value is estimated from the experimental band gaps value of the binary constituent CdTe [34] and ZnTe [35] as an average…”

Effect of applied hydrostatic pressure on the e–h ground transition in self‐assembled InAs/GaAs quantum lens

“…The band offset of the strained InAs/GaAs quantum lens where taken, for the conduction (valence) band, as 54% (46%) of the total band difference [5]. The temperature considered is T = 20 K. The variation of the effective masses was evaluated in terms of the fundamental gaps according to the Kane model [10][11][12]. The following variations are obtained:…”