Double exponential I-V characteristics and double Gaussian distribution of barrier heights in (Au/Ti)/Al sub(2)O sub(3)/n-GaAs (MIS)-type Schottky barrier diodes in wide temperature range

• Published in: Applied physics. A, Materials science & processing Vol. 122; no. 12; pp. 1 - 9
• Main Authors: Gueclue, Cigdem S, Oezdemir, Ahmet Faruk, Altindal, Semsettin
• Format: Journal Article
• Language: English
• Published: 01.12.2016
• Subjects: Aluminum oxide; Barriers; Constants; Deviation; Normal distribution; Slopes; Standard deviation; Voltage
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-016-0558-x

In this study, current conduction mechanisms of the sample (Au/Ti)/Al sub(2)O sub(3)/n-GaAs were investigated in detail using current-voltage (I-V) measurements in the temperature range of 80-380 K. The semilogarithmic I-V plots reveal two distinct linear regions with different slopes between 0.07-0.30 and 0.30-0.69 V which are called as Region I (RI) and Region II (RII), respectively. The ideality factor (n) and zero-bias barrier height (\(\varPhi_{\rm{bo}}\)) were found to be strong functions of temperature and voltage. In both regions, as the temperature increases, \(\varPhi_{\rm{bo}}\) increases, whereas the value of n decreases. The high value of n at low temperatures is an evidence of deviation from thermionic emission, and it cannot be explained solely by tunneling mechanism, the existence of surface states and interfacial layer. Therefore, the \(\varPhi_{\rm{bo}}\) versus q/kT plots were drawn for two linear regions of lnI-V plots, and these plots also revealed two distinct linear regions with different slopes between two temperature regions of 80-170 and 200-380 K which are called as low- and high-temperature range (LTR and HTR), respectively. Such behavior of these plots confirmed the existence of double Gaussian distribution (DGD) in the samples which in turn has mean barrier heights \(\bar{\varPhi}_{\text{bo}}\) and standard deviations ( sigma sub(s)). These values were obtained from the intercept and slope of these plots as 0.38 eV and 0.061 V for LTR and as 0.88 eV and 0.142 V for HTR (in RI), whereas they were obtained as 0.37 eV and 0.061 V for LTR and as 0.92 eV and 0.148 V for HTR (in RII), respectively. Thus, the modified ln(I sub(s)/T super(2))-q super(2) sigma sub(s) super(2) /2k super(2) T super(2) versus q/kT plots were drawn, and the values of (\(\bar{\varPhi}_{\text{bo}}\)) and effective Richardson constant (A super(*)) were extracted from the intercept and slope of these plots as 0.39 eV and 7.07 A/cm super(2) K super(2) for LTR and as 0.92 eV and 8.158 A/cm super(2) K super(2) for HTR (in RI), whereas they were extracted as 0.38 eV and 7.92 A/cm super(2) K super(2) for LTR and as 0.94 eV and 4.66 A/cm super(2) K super(2) for HTR (in RII), respectively. These values of A super(*) for two regions are close to the theoretical value (8.16 A/cm super(2) K super(2)) of n-type GaAs.