Low-temperature lattice thermal expansion of the II-VI semiconductor ZnSe

The low-temperature lattice thermal expansion of the wide gap semiconductor ZnSe is investigated using the quasi-harmonic theory of thermal expansion. The generalized Grüneisen parameters (GPs) of the elastic waves propagating in different directions with respect to the [001] crystallographic axis are calculated using the second-and third-order elastic constants. The values of the generalized GPs γj are generally positive except for γ2 from θ=25 to 65°. The Brugger gamma is calculated and the low-temperature limit of the Grüneisen gamma is determined using the procedure of Menon and Rao. The low-temperature limit γ¯ has been obtained as 0.46 for ZnSe. The volume expansion is expected to be positive down to absolute zero for ZnSe, since γ¯ is positive.