Aluminum schottky contacts to n-type 4H-SiC

Abstract

Aluminum Schottky contacts to n-type 4H-SiC were fabricated, and the results of electrical measurements on the devices are presented along with the Schottky barrier height and ideality factor. Furthermore, two different samples having different surface treatments were investigated. The barrier heights obtained from current-voltage (I-V) measurements on both samples are essentially identical, with an average value of 0.64 eV. The ideality factor of Sample 2, which had an HF-dip surface treatment, had an average value of 1.66. The ideality factor of Sample 1, which had a surface treatment similar to the other sample but with the addition of an RCA-like clean, had an average value of 2.60. Measurements on some control devices with Au contacts showed that no significant Fermi-level pinning occurred, and the barrier-height results for all devices approached the Schottky-Mott limit. Capacitance-voltage (C-V) measurements on the Al devices from Sample 1 yielded barrier heights that were much smaller than those obtained from the I-V curves; however, for Sample 2, the barrier heights obtained from both C-V and I-V methods were comparable. Based on these results, we propose a model that accounts for the measured results in terms of a thin interfacial layer produced in Sample 1, which screens the depletion region from the applied electric field. This model yields a possible explanation of how the two surface treatments result in devices with the same barrier height but different ideality factors. The results in this paper represent some of the first experimental data on Al/4H-SiC Schottky contacts.

The basic Schottky parameters for combined diffusion welded and sputter metal contacts

“…The direct comparison of barrier height (Pb, ideality factor i, the specific on-resistance Rsp between diffusion welded and sputter deposited Al contacts turned out to be rather difficult thing, because there are very few results on Al/4H-SiC contacts. Thus, in resent work [6] Harrell with co-authors gives for sputtered Al contacts to 4H-SiC the values of q ranged from 1.57 to 1.66 and 0b of 0.58 -0.69 eV. The results are close to ours, but it must be noted that for calculation of barrier height the authors used the Richardson's constant as 146…”

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.…”

Ohmic and rectifying contacts to n-SiC formed by energetic deposition of carbon

“…The range of metals successfully used to form ohmic contacts to n-SiC include Ni [2], Cr [3] and TiN [4] while examples of rectifying contacts have included Al [5], Au [6] and IrO 2 [7]. All ohmic contacts to n-SiC have required annealing at a temperature of > 600 ˚C to ensure a low specific contact resistance, ρ c .…”