Source of two-dimensional electron gas in unintentionally doped AlGaN/GaN multichannel high-electron-mobility transistor heterostructures

Abstract

Unintentionally doped (UID) AlGaN/GaN-based multichannel high electron mobility transistor (MC-HEMT) heterostructures have been demonstrated on the SiC substrate using plasma-assisted molecular beam epitaxy. The MC-HEMT heterostructure with a GaN channel thickness of 100 nm resulted in a cumulative two-dimensional electron gas (2DEG) concentration of 4.3 × 1013 cm−2 across six GaN channels. The sample showed sheet resistances of 170 Ω/sq. and 101 Ω/sq. at room temperature and 90 K, respectively. The source of 2DEG in the buried GaN channels of the heterostructure was investigated. The C–V measurements conducted on UID MC-HEMTs excluded the possibility of the valence band being the source of 2DEG and the consequent formation of two-dimensional hole gas at the buried GaN-channel/AlGaN-barrier interfaces. A comparison of the experimentally obtained 2DEG concentration with the simulated data suggests the presence of donor-like trap states, situated at 0.6 to 0.8 eV above the valence band at the buried GaN-channel/AlGaN-barrier interfaces, which act as the source of 2DEG in UID MC-HEMT heterostructures.

Current Drops in CF4 Plasma-Treated AlGaN/GaN Heterojunction in Polar Gas Ambient

“…This explains why the 2DEG sheet density of ~1 × 10 13 cm −2 not fully depleted by the higher F − sheet density of ~4.3 × 10 13 cm −2 . Although the origin of 2DEG in an AlGaN/GaN heterojunction is a controversial issue as yet, "ambient doping" sounds more reasonable, an states that "An important part of the origin of 2DEG in AlGaN/GaN heterojunction comes from the ambient doping [10,14,17]". The high concentration of 2DEG in the AlGaN/GaN heterojunction obtained from environmental doping is associated with surface states and surface ions [14].…”

Multidimensional device architectures for efficient power electronics

“…Multi-channel heterostructures reduce the sheet resistance (R SH ) by spreading a large 𝑛 into stacked channels with the 𝑛 in each channel not too high to compromise 𝜇 due to carrier scattering. The GaNbased multi-channel heterostructures can be either undoped [62][63][64][65] or doped, 36,43,66,67 and an R SH 3-10 times lower than the single-channel has been reported in both schemes. In an ideal undoped multi-channel, parallel 2DEGs and two-dimensional-hole gases (2DHGs) with equal 𝑛 are induced on the top and bottom sides of each GaN layer (Fig.…”

Analyzing the Electrical Characteristics of P-gate Enhanced HEMT with C-doped Buffer Layer through Silvaco

“…GaN has the advantages of large band gap, high electron mobility, low on-resistance and adjustable bandwidth, which makes it have broad application prospects in display lighting, 5G communication, power electronics, UV sterilization and other elds [1][2][3][4][5]. Due to the natural high-density two-dimensional electron gas (2DEG) at the AlGaN/GaN heterostructure interface, most of the GaN power devices currently under development are based on horizontal AlGaN/GaN high electron mobility transistors(HEMT).…”

“…Figure 3. shows the Mechanism of transfer about the peak electric eld at the edge of gate and drain in the off-state condition.…”