Gaussian distribution of barrier heights in (Ni/Au)/AlGaN/GaN-heterostructures from forward bias I-V-T measurements

Zeki, Tekeli; Şemsetin, Altındal; Mehmet, Çakmak; Süleyman, Özçelik; Mehmet Deniz, Çalışkan; Ekmel, Özbay Turkey

The forward bias current-voltage (I-V) characteristics of (Ni/Au)/AlGaN/GaN-heterostructures have been investigated in the temperature range of 295-415 K. The main diode parameters such as the ideality factor (n), zero-bias barrier height Φ_bo(I-V) and series resistance (Rs) were found strongly temperature dependent and while the Φ_bo(I-V) and Rs increases, the n decreases with increasing temperature. This behavior can be interrupt based on the assumption of a Gaussian distribution of barrier heights due to barrier height inhomogeneities that prevail at the interface. We attempted to draw a Φ_bo vs q/2kT plot to obtain evidence of a Gaussian distribution of the BHs , and the values of Φ_bo= 1.633 eV and σ_o= 0.215 V for the mean barrier height and standard deviation at zero bias, respectively, have been obtained from this plot. Thus, a modified ln(I_o/T²)-q²σ_o²/2(kT)² vs q/kT plot gives Φ_bo and Richardson constant A^* as 1.618 eV and 23.21 A/cm²K², respectively, without using the temperature coefficient of the barrier height. This value of the Richardson constant 23.21 A/cm²K² is very close to the theoretical value of 26.4 A/cm²K² for AlGaN/GaN. Hence, it has been concluded that the temperature dependence of the forward I-V characteristics of the (Ni/Au)/AlGaN/GaN-heterostructures can be successfully explained on the basis of TE mechanism with a Gaussian distribution of the barrier heights.

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