Compositional Dependence Of Band Gap Research Articles

Temperature and compositional dependence of the energy band gap of AlGaN alloys

Deep-ultraviolet photoluminescence spectroscopy has been employed to study the temperature and compositional dependence of the band gap of AlxGa1−xN alloys in the temperature range between 10 and 800 K. Band-edge emission peaks in AlxGa1−xN alloys were fitted by the Varshni equation to obtain Varshni coefficients, which increase nonlinearly with x. The values of Varshni coefficients obtained for GaN and AlN binary compounds in the present study are in good agreement with the previously reported values. Based on the experimental data, the compositional and temperature dependence of the band gap of AlxGa1−xN alloy has been empirically determined for the entire alloy range.

A study on barrier height of AuAl xGa 1 − xN Schottky diodes in the range 0 ≤ x ≤ 0.20

Schottky barrier contacts using Au and ohmic contact with Al were made on Al x Ga 1− x N grown by OMVPE in the composition range 0 ≤ x ≤ 0.20. All diodes were characterized between 77 and 373 K. Under forward bias the value of the ideality parameter n was found to be 1.04-2.40 at room temperature irrespective of the value of x. The barrier height ( Φ B ) of all diodes up to x = 0.20 was determined by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements. The relationship is nonlinear and Φ B was found to tend downward similar to the compositional dependence of band gap. Temperature dependence of n and Φ B and the values n > 1 are considered to be due to the spatial inhomogeneities of x at the metal-semiconductor interface. A difference in the values of Φ B determined by I- V and C- V measurements is attributed to the deformation of the spatial barrier distribution.