Zhernokletov Dmitry M, Negara Muhammad A, Long Rathnait D, Aloni Shaul, Nordlund Dennis, McIntyre Paul C
†Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
‡Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
ACS Appl Mater Interfaces. 2015 Jun 17;7(23):12774-80. doi: 10.1021/acsami.5b01600. Epub 2015 Jun 2.
We correlate interfacial defect state densities with the chemical composition of the Al2O3/GaN interface in metal-oxide-semiconductor (MOS) structures using synchrotron photoelectron emission spectroscopy (PES), cathodoluminescence and high-temperature capacitance-voltage measurements. The influence of the wet chemical pretreatments involving (1) HCl+HF etching or (2) NH4OH(aq) exposure prior to atomic layer deposition (ALD) of Al2O3 were investigated on n-type GaN (0001) substrates. Prior to ALD, PES analysis of the NH4OH(aq) treated surface shows a greater Ga2O3 component compared to either HCl+HF treated or as-received surfaces. The lowest surface concentration of oxygen species is detected on the acid etched surface, whereas the NH4OH treated sample reveals the lowest carbon surface concentration. Both surface pretreatments improve electrical characteristics of MOS capacitors compared to untreated samples by reducing the Al2O3/GaN interface state density. The lowest interfacial trap density at energies in the upper band gap is detected for samples pretreated with NH4OH. These results are consistent with cathodoluminescence data indicating that the NH4OH treated samples show the strongest band edge emission compared to as-received and acid etched samples. PES results indicate that the combination of reduced carbon contamination while maintaining a Ga2O3 interfacial layer by NH4OH(aq) exposure prior to ALD results in fewer interface traps after Al2O3 deposition on the GaN substrate.
我们使用同步辐射光电子发射光谱（PES）、阴极发光和高温电容 - 电压测量方法，将界面缺陷态密度与金属 - 氧化物 - 半导体（MOS）结构中Al2O3/GaN界面的化学成分相关联。研究了在n型GaN（0001）衬底上进行原子层沉积（ALD）的Al2O3之前，涉及（1）HCl + HF蚀刻或（2）NH4OH（水溶液）暴露的湿化学预处理的影响。在进行ALD之前，对经NH4OH（水溶液）处理的表面进行PES分析表明，与经HCl + HF处理的表面或原始表面相比，其Ga2O3成分更多。在酸蚀刻表面上检测到的氧物种表面浓度最低，而经NH4OH处理的样品显示出最低的碳表面浓度。与未处理的样品相比，两种表面预处理均通过降低Al2O3/GaN界面态密度改善了MOS电容器的电学特性。对于用NH4OH预处理的样品，在上带隙能量处检测到最低的界面陷阱密度。这些结果与阴极发光数据一致，表明与原始样品和酸蚀刻样品相比，经NH4OH处理的样品显示出最强的带边发射。PES结果表明，在ALD之前通过暴露于NH4OH（水溶液）来减少碳污染并同时保持Ga2O3界面层，会使Al2O3沉积在GaN衬底上后产生更少的界面陷阱。
