High-Performance AlGaN-Based Visible-Blind Resonant Cavity Enhanced Schottky Photodiodes
- PDF / 153,530 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 6 Downloads / 195 Views
C3.22.1
High-Performance AlGaN-Based Visible-Blind Resonant Cavity Enhanced Schottky Photodiodes Ibrahim Kimukin2, Necmi Biyikli1Tolga Kartaloglu1, Orhan Aytür1, and Ekmel Ozbay2 Department of Electrical and Electronics Engineering, Bilkent University, Bilkent, Ankara, 06800 TURKEY 2 Department of Physics, Bilkent University, Bilkent, Ankara 06800 TURKEY 1
ABSTRACT We have designed, fabricated and tested resonant cavity enhanced visible-blind AlGaNbased Schottky photodiodes. The bottom mirror of the resonant cavity was formed with a 20 pair AlN/AlGaN Bragg mirror. The devices were fabricated using a microwave compatible fabrication process. Au and indium-tin-oxide (ITO) thin films were used for Schottky contact formation. ITO and Au-Schottky devices exhibited resonant peaks with 0.153 A/W and 0.046 A/W responsivity values at 337 nm and 350 nm respectively. Temporal high-speed measurements at 357 nm resulted in fast pulse responses with pulse widths as short as 77 ps. The fastest UV detector had a 3-dB bandwidth of 780 MHz. INTRODUCTION Solar/visible-blind detection is vital for a number of critical applications including missile plume detection, flame/engine monitoring, chemical/biological agent sensing, and covert spaceto-space communications [1]. With its wide bandgap and intrinsic visible-blind absorption spectrum, AlxGa1-xN ternary alloy is the most promising material system for high-performance solar/visible-blind photodetectors [2]. High-performance ultraviolet (UV) detectors were reported using AlGaN-based Schottky [3]-[6], MSM [7]-[9], pin [10], [11], and avalanche type of photodiodes (PDs) [12]. These devices consisted of conventional, single-pass detector structures. On the other hand, resonant cavity enhanced (RCE) detector structure offers selective enhancement of device responsivity [13]. The RCE-PD exhibits a multi-pass detection scheme at the cavity resonance wavelengths, which leads to improved efficiency performance. High performance infrared RCE-PDs using AlGaAs and InGaAs material systems were previously reported [14]-[16]. Recently, Kishino et al. have demonstrated the first UV RCE-PD with an AlGaN-based MSM PD, where they have reported resonant peaks around 360 nm [17]. In this paper, we report on the design, fabrication, and characterization of high-speed RCE AlGaN Schottky PDs. Au and ITO-Schottky devices were fabricated and compared in terms of detector performance. A peak responsivity of 0.153 A/W at 337 nm and a 3-dB bandwidth of 780 MHz were obtained with ITO and Au-Schottky RCE-PDs respectively. DESIGN AND FABRICATION For the design of the RCE-PD structure, a transfer-matrix-method (TMM) based simulation program was used. The detector was designed to achieve a resonant enhancement around 350 nm. The spectral complex refractive index data of AlxGa1-xN needed for the simulations were obtained from Ref. 18. Figure 1(a) shows the epitaxial layer structure of the designed RCE-PD wafer. A lightly doped (n=5×1016 cm-3) 70 nm thick GaN absorption layer was used as the
Downloaded from https://w
Data Loading...
