Double Gaussian distribution of barrier heights and self-powered infrared photoresponse of InN/AlN/Si (111) heterostructure

In this work, we have investigated the electrical characteristics of Au–Cu–n-InP Schottky contacts by current–voltage (I–V) and capacitance–voltage (C–V) measurements in the temperature range 260–420 K in steps of 20 K. The diode parameters, such as the ideality factor, n, and zero-bias barrier height, Φb0, have been found to be strongly temperature dependent. It has been found that the zero-bias barrier height, Φb0(I–V), increases and the ideality factor, n, decreases with an increase in temperature. The forward I–V characteristics are analyzed on the basis of standard thermionic emission (TE) theory and the assumption of gaussian distribution of barrier heights, due to barrier inhomogeneities that prevail at the metal–semiconductor interface. The zero-bias barrier height Φb0 versus 1/2kT plot has been drawn to obtain the evidence of a gaussian distribution of the barrier heights. The corresponding values are Φb0 = 1.16 eV and σ0 = 159 meV for the mean barrier height and standard deviation, respectively. The modified Richardson plot has given mean barrier height, Φb0, and Richardson constant, A**, as 1.15 eV and 7.34 Acm−2K−2, respectively, which is close to the theoretical value of 9.4 Acm−2K−2. Barrier heights obtained from C–V measurements are higher than those obtained from I–V measurements. This inconsistency between Schottky barrier heights (SBHs) obtained from I–V and C–V measurements was also interpreted. The temperature dependence of the I–V characteristics of the Au–Cu–n-InP Schottky diode has been explained on the basis of TE mechanism with gaussian distribution of the SBHs.

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Study of long-term flux and photon index distributions of blazars using RXTE observations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3108 ◽

2019 ◽

Vol 491 (2) ◽

pp. 1934-1940 ◽

Cited By ~ 1

Author(s):

Rukaiya Khatoon ◽

Zahir Shah ◽

Ranjeev Misra ◽

Rupjyoti Gogoi

Keyword(s):

Gaussian Distribution ◽

Lognormal Distribution ◽

Flux Distribution ◽

High Energy ◽

X Rays ◽

Photon Index ◽

Double Gaussian Distribution ◽

The Difference ◽

Anderson Darling ◽

Bl Lacs

ABSTRACT We present a detailed study of flux and index distributions of three blazars [one flat-spectrum radio quasar (FSRQ) and two BL Lacertae objects (BL Lacs)] by using 16 yr of Rossi X-ray Timing Explorer (RXTE) archival data. The three blazars were chosen such that their flux and index distributions have sufficient number of data points (≥90) with relatively less uncertainty $\left(\overline{\sigma _{\rm err}^{2}}/\sigma ^{2} < 0.2\right)$ in light curves. Anderson–Darling (AD) test and histogram fitting show that flux distribution of FSRQ 3C 273 is lognormal, while its photon index distribution is Gaussian. This result is consistent with linear Gaussian perturbation in the particle acceleration time-scale, which produces lognormal distribution in flux. However, for two BL Lacs, viz. Mrk 501 and Mrk 421, AD test shows that their flux distributions are neither Gaussian nor lognormal, and their index distributions are non-normal. The histogram fitting of Mrk 501 and Mrk 421 suggests that their flux distributions are more likely to be a bimodal, and their index distributions are double Gaussian. Since, Sinha et al. had shown that Gaussian distribution of index produces a lognormal distribution in flux, double Gaussian distribution of index in Mrk 501 and Mrk 421 indicates that their flux distributions are probably double lognormal. Observation of double lognormal flux distribution with double Gaussian distribution in index reaffirms two flux states hypothesis. Further, the difference observed in the flux distribution of FSRQ (3C 273) and BL Lacs (Mrk 501 and Mrk 421) at X-rays suggests that the low-energy emitting electrons have a single lognormal flux distribution, while the high-energy ones have a double lognormal flux distribution.

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