| Abstract [eng] |
Various types of detectors are employed for this region, but only a small fraction work at the room temperature with high enough response speed for real time operation. Bow-tie (BT) diodes fabricated on structures with two dimensional electron gases (2DEG) meet all of the criteria mentioned above. Previously research on BT diode detectors focused mostly on GaAs family material [1]–[3], in part to very high electron mobility in these materials. Recently research on BT diodes fabricated on AlGaN/GaN high electron mobility transistor (HEMT) structures also appeared [4]. Nitride HEMT structures have many advantages over arsenide materials: higher carrier concentrations in 2DEG layer, GaN has much shorter electron energy relaxation time, higher resistance to chemical and mechanical damage. The aim of this work is to fabricate BT diodes on commercial Al0.25Ga0.75N/GaN HEMT structure and study their response at the room temperature in the frequency range of 0,1 – 0,6 THz. The 2DEG electron density and carrier mobility were found to be nearly 1∙1013 cm-2 and 1900 cm2 V 1 s 1. Responsivity of BT diodes was investigated in several ways. Firstly, it was found that decreasing of BT diode apex width from 17 μm to 2 μm resulted in non-linear increase in responsivity for detection of both 0,15 THz and 0,3 THz radiation. Secondly, response of BT diodes was found to be linearly dependent on absorbed radiation power and could be increased 7 times with 1,5 V DC voltage bias. Furthermore, three designs of antenna integrated BT diodes are compared – A1 (bow-tie antenna), A2 (dipole antenna), A3 (H type antenna). Overall, highest optical responsivity of 3±1,6 V/W was achieved for A1 type antennas for 0,15 THz. A2 and A3 antenna integrated BT diodes were more responsive for 0,3 THz and best results were obtained for dipole type (A2) antenna, for which responsivity of 0,40±0,07 V/W at 0,3 THz was achieved. [1] D. Seliuta et al., „Detection of terahertz∕sub-terahertz radiation by asymmetrically-shaped 2DEG layers“, Electron. Lett., t. 40, nr. 10, p. 631, 2004. [2] I. Kašalynas, R. Venckevičius, G. Valušis, „Continuous Wave Spectroscopic Terahertz Imaging With InGaAs Bow-Tie Diodes at Room Temperature“, IEEE Sens. J., t. 13, nr. 1, p. 50–54, saus. 2013. [3] V. Palenskis et al., „InGaAs Diodes for Terahertz Sensing—Effect of Molecular Beam Epitaxy Growth Conditions“, Sensors, t. 18, nr. 11, p. 3760, lapkr. 2018. [4] V. Jakštas et al., „Development of the terahertz bow-tie diodes of AlGaN/GaN-heterostructures with high mobility 2DEG“, 2017 42nd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2017, p. 1–2. |
