Fixed charge in high-k/GaN metal-oxide-semiconductor capacitor structures

Interface charge engineering at atomic layer deposited dielectric/III-nitride interfaces

“…Metal-insulator-semiconductor HEMTs (MISHEMTs) [8][9][10][11][12][13][14][15][16][17][18][19] structure can efficiently suppress gate leakage in transistors scaled to achieve higher frequency operation and could also be used for applications in GaN power switching. 1,3 The interface trap density and related dispersion in atomic layer deposited (ALD) dielectric/III-nitride interfaces are significantly lower than in III-As semiconductors, 20,21 but recent work has shown that a high density of fixed charges of the order of 1 lC/cm 2 is induced at ALD-grown Al 2 O 3 /GaN and Al 2 O 3 /AlN structures, [22][23][24] an effect that is unique among previously investigated semiconductor material systems. While this charge is not modulated by gate voltage and does not lead to hysteresis under normal device operation, it does significantly modify the electrostatics in the system.…”

Preparation of gallium nitride surfaces for atomic layer deposition of aluminum oxide

“…The two groups of samples (with/without (NH 4 ) 2 S dip) were further divided based on two types of in situ dry cleaning: those which received 5 cycles of TMA and those which received 5 cycles of atomic hydrogen/TMA/atomic hydrogen prior to the start of deposition which is identical to the in situ H/TMA/H method reported by Son et al 33 In total, this produced four distinct combinations of wet and dry ALD pretreatments which have been denoted by letters A-D. A summary of these treatments is shown in Table I. The in situ treatments were performed in the ALD chamber (Oxford Instruments FlexAl ALD) at a temperature of 300…”

“…• C. For the pretreatments, each TMA cycle consisted of a 40 ms pulse at a pressure of 200 mTorr with Ar carrier gas flow of 100 sccm followed by a 5 s Ar purge, and finally a H 2 gas stabilization step for 10 s. 34,33 Each atomic hydrogen pulse was generated using an Oxford FlexAl plasma source with an ICP forward power of 100 W and consisted of exposure to the plasma for 2 s at a H 2 pressure of 20 mTorr.…”

Correlation of interface states/border traps and threshold voltage shift on AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors

“…The different V TH values are most probably due to the different fixed charges brought by different gate dielectrics. 12 The frequency-dependent conductance technique was proposed by Nicollian and Goetzberger 13 and has been successfully applied to characterize the interface states for depletion-mode (D-mode) AlGaN/GaN MIS-HEMTs. 6,7 Considering the case in AlGaN/GaN MIS-HEMTs, a positive gate bias is needed to transfer the electrons from the channel to the interface between the AlGaN barrier and the gate dielectric where electrons might be trapped at interface states.…”