Enhancement of two dimensional electron gas concentrations due to Si3N4 passivation on Al0.3Ga0.7N/GaN heterostructure: strain and interface capacitance analysis

Abstract

Enhancement of two dimensional electron gas (2DEG) concentrations at Al0.3Ga0.7N/GaN hetero interface after a-Si3N4 (SiN) passivation has been investigated from non-destructive High Resolution X-ray Diffraction (HRXRD) analysis, depletion depth and capacitance-voltage (C-V) profile measurement. The crystalline quality and strained in-plane lattice parameters of Al0.3Ga0.7N and GaN were evaluated from double axis (002) symmetric (ω-2θ) diffraction scan and double axis (105) asymmetric reciprocal space mapping (DA RSM) which revealed that the tensile strain of the Al0.3Ga0.7N layer increased by 15.6% after SiN passivation. In accordance with the predictions from theoretical solution of Schrödinger-Poisson’s equations, both electrochemical capacitance voltage (ECV) depletion depth profile and C-V characteristics analyses were performed which implied effective 9.5% increase in 2DEG carrier density after passivation. The enhancement of polarization charges results from increased tensile strain in the Al0.3Ga0.7N layer and also due to the decreased surface states at the interface of SiN/Al0.3Ga0.7N layer, effectively improving the carrier confinement at the interface.

Reactive evaporation of SiOx films for passivation of GaN high-electron-mobility transistors

“…The increase in the 2DEG density could be due to reduced surface traps by the passivation. Another factor may be passivation induced stress in the AlGaN layer which changes the piezoelectric polarization in the AlGaN/AlN/GaN heterostructure [33,34].…”

Confinement of Electrons at the LaInO3/BaSnO3 Heterointerface

“…[25] A more direct approach, that can extract depth-resolved carrier concentration profiles, are C-V measurements. [26] Such measurements have been routinely used to investigate the accumulation of electrons in (Al,Ga)N/GaN heterostructures, [27][28][29] and are applied here with the coplanar contact geometry presented in Figure 4a on the samples with 0.4% and 0.35% La-doping of the BaSnO 3 channel layer after the deposition of 10 nm thick LaInO 3 .…”

“…In the resulting C-V curves of both samples shown in Figure 4b, it can be observed, that the capacitance is nearly constant for a voltage interval between 1 and −1.5 V (0.35%) or −3 V (0.40%) followed by a strong decrease to almost zero for larger negative bias. Such a behavior indicates an accumulation of electrons in a thin layer, such as a 2DEGs in (Al,Ga)N/GaN heterostructures [27][28][29] and its full depletion toward large negative bias. The integral of the C-V curves yields the total sheet electron concentration of ≈10 13 cm −2 depleted during the voltage sweep for both samples, of which most is located under the plateau, i.e., in the 2DEG.…”

Effect of PECVD SiNx deposition process parameters on electrical properties of SiNx/AlGaN/GaN structures

“…It was shown [3] that the synthesized dielectric film may have internal mechanical stresses of about 300-600 MPa which is an order of magnitude lower than the stress in the AlGaN buffer layer caused by the lattice mismatch between buffer layer and the underlying GaN layer. High resolution X-ray diffraction showed [7] that PECVD of a 40 nm SiN x film increases the tensile stress in the AlGaN layer by 15%, the carrier concentration in the 2D electron gas (2DEG) channel increasing by 9,5%. The positive fixed charge estimated, e.g.…”

“…Electric states generated at the dielectric/semiconductor interface during the formation of protective coatings are of a great interest. Parameters of film/heterostructure surface interface were analyzed [1][2][3][4][5][6][7][8][9][10], including the possibility of the formation of donor-like trapping centers due to the impact of plasma ions during PECVD processes. It was reported [8] that there are but a few trapping states in the dielectric film bulk: these states locate very close to the dielectric/semiconductor interface.…”