Surface donor states distribution post SiN passivation of AlGaN/GaN heterostructures

Abstract

In this paper, we present a physics based analytical model to describe the effect of SiN passivation on two-dimensional electron gas density and surface barrier height in AlGaN/GaN heterostructures. The model is based on an extraction technique to calculate surface donor density and surface donor level at the SiN/AlGaN interface. The model is in good agreement with the experimental results and promises to become a useful tool in advanced design and characterization of GaN based heterostructures.

Analytical modeling of AlGaN/AlN/GaN heterostructures including effects of distributed surface donor states

“…11 The same therefore applies to SiN passivated AlGaN/AlN/GaN structures, since both have a SiN/AlGaN interface. Moreover, the model parameter values for the surface donor states will be the same, provided the Al mole fraction in their Al x Ga 1Àx N layer is the same.…”

“…The model was subsequently applied also to structures with SiN passivated surfaces. 11 Here, we present an extension of this model to the AlGaN/AlN/GaN heterostructures. We start with schematic comparison of its band diagram with that of the AlGaN/GaN structure in Fig.…”

“…[2][3][4][5][6][7][8] In a simple two-parameter model, 8 the distribution of the surface donor states are described by the surface donor level (E d ) relative to the conduction band minimum at the AlGaN surface, and the surface donor density (n o ). These parameters are strongly dependent on the Al mole fraction in the AlGaN barrier layer and on the type of surface interface, i.e., on whether we have a bare surface, 7,8 a surface passivation, [9][10][11] or a metal. 12 In any case, the surface states strongly influence important, observable device properties such as the AlGaN surface barrier height and the 2DEG density, as described in a previous study.…”

Interface Si donor control to improve dynamic performance of AlGaN/GaN MIS-HEMTs

“…Goyal et al 20 also showed that SiN x passivation enhances the interface donor density. It has been reported that the LPCVD-SiN x can suppress deep states at the SiN x /HEMT interface, [21][22][23] and it was adopted to fabricate high-performance normally off MIS-HEMTs maybe using the Si doping effect of LPCVD.…”

“…[15][16][17] Si donors have been proved to be one of the causes of 2DEG variation from theory and experiment due to Gauss's law and charge neutrality principle. 6,16,[18][19][20] Onojima et al 16 speculated that Si atoms at the SiN x /AlGaN interface might act as donors, which partially neutralize negative polarization charges at the AlGaN surface, and lead to a reduction in the AlGaN potential barrier height, thereby increasing 2DEG density.…”