Electrical characteristics of Mo/4H-SiC Schottky diodes having ion-implanted guard rings: temperature and implant-dose dependence

Abstract

The electrical characteristics of ion-implanted guard rings for molybdenum (Mo) Schottky diodes on 4H-SiC are analyzed on the basis of the standard thermionic emission model and the assumption of a Gaussian distribution of the barrier height. For edge termination, high-resistivity guard rings manufactured by carbon and aluminum ion-implanted areas were used. Extractions of barrier heights of molybdenum on silicon carbide (4H-SiC) Schottky diodes have been performed on structures with various gate metallization, using both current-voltage-temperature (I-V-T) and capacitance-voltage (C-V) measurements. Characteristic features of the Schottky barrier height (SBH) are considered in relation to the specific dose of the carbon-or aluminum-implanted guard ring. Contacts showed excellent Schottky behavior ideality factors between 1.02 and 1.24 in the range of 303-473 K. The measured SBHs were between 0.92 and 1.17 eV in the same temperature range from I-V-T characteristics. The variations in the barrier height, which is significantly temperature-and implantation-dose-dependent, are well fitted to a single Gaussian distribution function. Experimental results agree reasonably well by using this approach, particularly for carbon implantation dose of 1.75 × 10 14 cm −2 , and a mean barrier height ( ¯ B0 ) of 1.22 eV and zero bias standard deviation σ 0 = 0.067 V have been obtained. Furthermore, the modified Richardson plot according to the Gaussian distribution model resulted in a mean barrier height ( ¯ B0 ) and a Richardson constant (A * ) of 1.22 eV and 148 A cm −2 K −2 , respectively. The A * value obtained from this plot is in very close agreement with the theoretical value of 146 A cm −2 K −2 for n-type 4H-SiC. Therefore, it has been concluded that the temperature dependence of the forward (I-V) characteristics of the Mo/4H-SiC contacts can be successfully explained on the basis of a thermionic emission conduction mechanism with Guassianly distributed barriers.

Temperature dependence of current-and capacitance–voltage characteristics of an Au/4H-SiC Schottky diode

“…However, the current transport properties of SiC remain still as a topic which is interested. In the literature, it is seen frequently that the researches connected with SiC Schottky rectifiers have majored on 4H-SiC [11][12][13][14][15][16][17][18][19][20][21][22][23][24] and 6H-SiC [15,[25][26][27][28]. However, 4H-SiC is preferred due to the isotropic nature of its electrical properties, and the fact that, the electron mobility of 4H-SiC is twice that of 6H-SiC [4,29].…”

“…In the literature, different metals such as the aluminum [11,12], tungsten (W) [13], titanium (Ti) [14][15][16][17][18][19], nickel (Ni) [14,16,20,21], molybdenum (Mo) [22,23] have been used by the various authors to fabricate Schottky contacts on 4H-SiC. However, Au as a refractory metal on 4H-SiC was used in limited number [24] as we know.…”

Electronic transport of Au/(Ca1.9Pr0.1Co4Ox)/n-Si structures analysed over a wide temperature range

“…These measurements, when carried out over a wide temperature range, better reveal various aspects on the conduction mechanism and the nature of BH [10][11][12][13][14]. Many previous studies have found increases in the BH and decreases in n with increasing temperature [4][5][6][7][8][10][11][12][13][14][15][16], in disagreement with the predictions of the standard TE theory of temperature-independent BH and ideality factor. In the last two decades, both the abnormal behaviour of the BH and the nonlinearity of the Richardson plot have been observed [17][18][19][20][21][22].…”

“…It is clear that the FE and TFE mechanisms are ruled out in the whole temperature range (120-360 K) because the slope of ln (I) vs. V or nT is not constant in the whole measured temperature range. All these results show that the value of n and tunnelling factor (χ 0.5 δ) should also be included in the expression for I o as in the following relation [7,32]:…”

“…Although there are many studies both theoretical and experimental on these devices, their conduction mechanisms and the formation of barrier height (BH) at MIS interface have not been clarified yet [1][2][3][4][5][6][7][8][9]. At any specific, especially low-temperature and -voltage, interval several conduction mechanisms can be individually dominating or collectively operative.…”