Demonstration of UV-Induced Threshold Voltage Instabilities in Vertical GaN Nanowire Array-Based Transistors

Abstract

This paper investigates the degradation of vertically aligned gallium nitride (GaN) nanowire (NW) arrays submitted to gate bias stress and UV light. Based on electrical tests and simulations, we demonstrate the existence of trapping processes that depend on the applied stress voltage V Gstress and on the applied light during stress (wavelength, λ). We demonstrate the following original results: 1) for positive and negative V Gstress conditions, no significant variation in dc characteristics is observed when the samples are stressed in dark and 2) when the devices are submitted to negative V Gstress and to UV light, a positive variation in threshold voltage (V th) is observed. The positive V th shift is ascribed to the transfer and trapping of electrons from the gate metal to the oxide, promoted by UV light. We also evaluated the temperature dependence of the threshold voltage shift under UV light. We demonstrated an increased trapping at higher temperatures, indicating a role of thermionic processes in electron trapping. On the other hand, detrapping from oxide states proceeds through defect-mediated conduction, i.e., is limited by the number of available states.

Analysis of High-Frequency Behavior of AlGaN/GaN HEMTs and MIS-HEMTs under UV Illumination

“…The dc and transient characteristics of GaN-based HEMTs under UV illumination have been investigated widely to demonstrate the photoconductivity and spectral responsivity as well as to explore the charge trapping phenomena in devices. [10][11][12][13][14][15] However, the highfrequency behavior of GaN-based HEMTs under UV illumination was less discussed. With the high optical response and excellent microwave performance, GaN-based devices should be suitable for using in optically controlled and optically switched integrated circuits.…”

Ultrashort Pulse Laser Lift-Off Processing of InGaN/GaN Light-Emitting Diode Chips

“…Nonetheless, in case of many defects presented in the material (e.g., the condition of the GaN surface after ICP-RIE shown in Figure S1), a higher number in dangling or defective Ga bonds generate local etch pit formation. This has led to an opportunity for hydroxide ions to reach Ga atoms in defect-rich areas progressing the wet etching process. , More detailed explanation and characteristics of this hybrid etching method combining both ICP-RIE and KOH-based wet etching processes on different stacks of GaN layers have been described in our former studies and the reports from other groups. − We have also demonstrated to employ this hybrid etching technique for realizing both field-effect transistors and LEDs based on vertical GaN nanowire arrays. ,,, …”