Light Influence on the Sheet Resistance of AlGaN/GaN Heterostructures Grown by MOVPE Technique

Sheet resistance is the most commonly used electrical parameters of thin films; the special feature of sheet resistance is its scalability that is often used in the qualitative assessment of its usefulness. That is why it is so often used as an electrical parameter in the evaluation of created layers by various epitaxial methods. In materials based on AIIIN compounds, there is a built-in electric field that disturbs the electrical charge inside the heterostructure. The perturbed distribution of electrical charge inside the heterostructure creates donor states on the surface that increase the surface resistance value. The paper presents the influence of UV radiation on surface states affecting the sheet resistance of AlGaN/GaN heterostructures. Based on the presented method, influence of light on sheet resistance is examined and spectral characteristics of AlGaN/GaN heterostructure are obtained. Measurements are performed using the Hall Bar test structure fabricated in AlGaN/GaN heterostructure grown by metal organic vapor phase epitaxy methods. The Hall bar test structures are investigated at room temperature under the light excitation in the range from 280 to 640 nm.