Demonstration of Al_<i>X</i>Ga_1−<i>X</i>N Solar-Blind UV Phototransistor With Double Heterostructures and Winding Gate

We have demonstrated a solar-blind ultraviolet (UV) phototransistor (PT) equipped with Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>y</i></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>1</roman>-<i>y</i></sub>N/Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>1</roman>-<i>x</i></sub>N/Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>z</i></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>1</roman>-<i>z</i></sub>N double heterostructures and winding gate configuration. There exists a 2-D electron gas (2DEG) at Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>0</roman>.<roman>55</roman></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>0</roman>.<roman>45</roman></sub>N/Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>0</roman>.<roman>4</roman></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>0</roman>.<roman>6</roman></sub>N heterointerface, due to the intrinsic polarization effect of Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>1</roman>-<i>x</i></sub>N. The Ni/Au metal stacks are deposited between two-sided interdigital Ohmic electrodes to form a Schottky gate. The gate can act as a switch to close or open the conduction channel between source and drain by the regulation of the 2DEG density. Thus, when given a specific negative gate voltage, the fabricated PT exhibits a photocurrent-to-dark-current ratio (PDCR) of 2.24 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sup> and a high responsivity of 1.86 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>3</roman></sup> A/W under 280 nm UV illumination at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>ds</roman></sub> = 2 V, a high specific detectivity of 5.84 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><roman>14</roman></sup> Jones included, implying outstanding ability to detect solar-blind UV. Besides, to grasp the underlying mechanism of gate control and double heterostructures, comprehensive 2-D device simulations have performed, revealing that the variation trends of energy band and electron concentration are affected by the applied negative gate bias and incident light.