Retardation Mechanism of Ultrathin Al₂O₃ Interlayer on Y₂O₃ Passivated Gallium Nitride Surface

Abstract

A systematic investigation was carried out by incorporating an ultrathin aluminum oxide (Al2O3) as an interlayer between yttrium oxide (Y2O3) passivation layer and GaN substrate. The sandwiched samples were then subjected to postdeposition annealing in oxygen ambient from 400 to 800 °C. The Al2O3 interlayer was discovered to play a significant role in slowing down inward diffusion of oxygen through the Y2O3 passivation layer as well as in impeding outward diffusion of Ga(3+) and N(3-) from the decomposed GaN surface. These beneficial effects have suppressed subsequent formation of interfacial layer. A mechanism in association with the function of Al2O3 as an interlayer was suggested and discussed. The mechanism was explicitly described on the basis of the obtained results from X-ray diffraction, X-ray photoelectron spectroscopy, energy-filtered transmission electron microscopy (TEM), high resolution TEM, and electron energy loss spectroscopy line scan. A correlation between the proposed mechanism and metal-oxide-semiconductor characteristics of Y2O3/Al2O3/GaN structure has been proposed.

Preparation and characterisation of aluminium zirconium oxide for metal‐oxide‐semiconductor capacitor

“…20 Hence, an improvement in MOS characteristics of Y 2 O 3 /Al 2 O 3 stacking structure on GaN substrate was attained when compared with single Y 2 O 3 passivation layer. 20,27 It was also reported that the passivating properties of ZrO 2 layer was enhanced through the doping of Al 2 O 3 into ZrO 2 lattice, where in Al 2 O 3 doped ZrO 2 passivating layer has demonstrated leakage current density of approximately 10 −7 A/cm 2 at gate voltage of 1 V, which was relatively low. Besides, flat band voltage shift of approximately 0.2 V, which was relatively small with a hysteresis lesser than 10 mV were also reported.…”

“…The existence of defects might be useful for the above applications yet the employment of ZrO 2 as the passivation layer on Si was confronted with a small conduction band offset ( 1.40 eV) [15][16] as well as moderate k-value (k = 8-10). [19][20][21] In order to prevail over the short comings, different stacking combinations of ZrO 2 /Al 2 O 3 and Al 2 O 3 /ZrO 2 structures have been exploited with an intention of mitigating the diffusivity rate of oxygen to the Si surface. [21][22][23] Al 2 O 3 is unique because of oxygen interstitials found in the Al 2 O 3 lattice that tended to curb oxygen diffusion to the Si surface and thus retarding interfacial layer formation.…”

“…[21][22][23] Al 2 O 3 is unique because of oxygen interstitials found in the Al 2 O 3 lattice that tended to curb oxygen diffusion to the Si surface and thus retarding interfacial layer formation. 20,[24][25][26] Likewise, the interstitial sites in Al 2 O 3 lattice restrained also the diffusion of nitrogen and gallium species from the decomposed GaN surface to Y 2 O 3 passivation layer and thereby minimising the generation of defect states in the Y 2 O 3 passivation layer. 20 Hence, an improvement in MOS characteristics of Y 2 O 3 /Al 2 O 3 stacking structure on GaN substrate was attained when compared with single Y 2 O 3 passivation layer.…”

“…20,[24][25][26] Likewise, the interstitial sites in Al 2 O 3 lattice restrained also the diffusion of nitrogen and gallium species from the decomposed GaN surface to Y 2 O 3 passivation layer and thereby minimising the generation of defect states in the Y 2 O 3 passivation layer. 20 Hence, an improvement in MOS characteristics of Y 2 O 3 /Al 2 O 3 stacking structure on GaN substrate was attained when compared with single Y 2 O 3 passivation layer. 20,27 It was also reported that the passivating properties of ZrO 2 layer was enhanced through the doping of Al 2 O 3 into ZrO 2 lattice, where in Al 2 O 3 doped ZrO 2 passivating layer has demonstrated leakage current density of approximately 10 −7 A/cm 2 at gate voltage of 1 V, which was relatively low.…”

Comparative study of oxidizing ambient infused with varying nitrogen flow rates for fabrication of ternary nitrided AlZrO based MOS capacitor

“…The ease of crystallization in ZrO 2 on the other hand was giving con as a high k metal oxide, owing to the formation of grain boundaries, which would serve as a leakage current path 5 . Thus, an alternative route has been implemented by incorporating Al 2 O 3 into ZrO 2 , with the aim to increase crystallization temperature of ZrO 2 while not sacrificing the high k value of ZrO 2 since ZrO 2 possesses a higher k value than Al 2 O 3 ( k = 8‐10) 6 …”