Deyu Getnet Kacha, Hunka Jonas, Roussel Hervé, Brötz Joachim, Bellet Daniel, Klein Andreas
Electronic Structure of Materials, Department of Materials and Earth Sciences, Technische Universität Darmstadt, Otto-Berndt-Straße 3, 64287 Darmstadt, Germany.
Univ. Grenoble Alpes, CNRS, Grenoble INP, LMGP, 38 000 Grenoble, France.
Materials (Basel). 2019 Jul 11;12(14):2232. doi: 10.3390/ma12142232.
Low-temperature-processed ITO thin films offer the potential of overcoming the doping limit by suppressing the equilibrium of compensating oxygen interstitial defects. To elucidate this potential, electrical properties of Sn-doped In 2 O 3 (ITO) thin films are studied in dependence on film thickness. In-operando conductivity and Hall effect measurements during annealing of room-temperature-deposited films, together with different film thickness in different environments, allow to discriminate between the effects of crystallization, grain growth, donor activation and oxygen diffusion on carrier concentrations and mobilities. At 200 ∘ C , a control of carrier concentration by oxygen incorporation or extraction is only dominant for very thin films. The electrical properties of thicker films deposited at room temperature are mostly affected by the grain size. The remaining diffusivity of compensating oxygen defects at 200 ∘ C is sufficient to screen the high Fermi level induced by deposition of Al 2 O 3 using atomic layer deposition (ALD), which disables the use of defect modulation doping at this temperature. The results indicate that achieving higher carrier concentrations in ITO thin films requires a control of the oxygen pressure during deposition in combination with seed layers to enhance crystallinity or the use of near room temperature ALD.
低温处理的氧化铟锡（ITO）薄膜具有通过抑制补偿性氧间隙缺陷的平衡来克服掺杂极限的潜力。为了阐明这种潜力，研究了掺锡氧化铟（ITO）薄膜的电学性质与薄膜厚度的关系。对室温沉积薄膜退火过程中的原位电导率和霍尔效应测量，以及在不同环境下不同薄膜厚度的测量，有助于区分结晶、晶粒生长、施主激活和氧扩散对载流子浓度和迁移率的影响。在200℃时，通过掺入或提取氧来控制载流子浓度仅在非常薄的薄膜中占主导地位。室温下沉积的较厚薄膜的电学性质主要受晶粒尺寸的影响。在200℃时，补偿性氧缺陷的剩余扩散率足以屏蔽使用原子层沉积（ALD）沉积Al2O3所诱导的高费米能级，这使得在此温度下无法使用缺陷调制掺杂。结果表明，在ITO薄膜中实现更高的载流子浓度需要在沉积过程中控制氧压，并结合籽晶层以提高结晶度，或者使用近室温的ALD。
