Metal-Semiconductor-Metal (MSM) Photodetectors Based on Single-walled Carbon Nanotube Film-GaAs Schottky Contacts
- PDF / 1,762,007 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 75 Downloads / 196 Views
1057-II22-05
Metal-Semiconductor-Metal (MSM) Photodetectors Based on Single-walled Carbon Nanotube Film-GaAs Schottky Contacts Jason L. Johnson1, Ashkan Behnam1, Yongho Choi1, Leila Noriega1, Gunhan Ertosun2, Zhuangchun Wu3, Andrew G. Rinzler3, Pawan Kapur2, Krishna C. Saraswat2, and Ant Ural1 1 Electrical and Computer Engineering, University of Florida, Gainesville, FL, 32611 2 Department of Electrical Engineering, Stanford University, Stanford, CA, 94305 3 Department of Physics, University of Florida, Gainesville, FL, 32611 ABSTRACT We experimentally study the dark and photocurrent in metal-semiconductor-metal (MSM) photodetectors based on single-walled carbon nanotube film Schottky contacts on GaAs. We find that above ~260°K, thermionic emission of electrons with a barrier height of ~0.54 eV is the dominant dark current transport mechanism. Furthermore, MSM devices with CNT film electrodes exhibit a higher photocurrent-to-dark current ratio while maintaining a comparable responsivity relative to control devices. This work demonstrates that nanotube films can be integrated as Schottky electrodes in conventional semiconductor optoelectronic devices.
INTRODUCTION AND BACKGROUND A single-walled carbon nanotube (CNT) film consists of an interwoven mesh of carbon nanotubes and exhibits uniform physical/electronic properties independent of the diameter, chirality, location, and direction of individual tubes making up the film due to ensemble averaging [1-3]. As a result, it is highly manufacturable compared to individual CNTs, which have traditionally been plagued by process control issues [4]. Furthermore, the CNT film is conductive and transparent [1-3,5], making it promising for applications as contacts in optoelectronic and photovoltaic devices, such as light-emitting diodes (LEDs) [6-9], organic solar cells [10-13], and electrochromic devices [14]. Recently, CNT films have been used as ohmic contacts on GaN [6] and organic materials [7-12] in LEDs and solar cells. However, optoelectronic devices where the CNT film is used as a Schottky contact have not been previously demonstrated. Here, we demonstrate the Schottky behavior of CNT film contacts on GaAs by fabricating and characterizing Metal-Semiconductor-Metal (MSM) photodetectors with CNT film electrodes. We extract the Schottky barrier height of the CNT film on GaAs by studying the temperature-dependence of the dark current of the fabricated MSM devices. We find that thermionic emission of electrons over a Schottky barrier of height φ Bn ≈ 0.54 eV is the dominant transport mechanism in CNT film-GaAs metal-semiconductor (M-S) junctions at temperatures above 260oK. Assuming an ideal M-S diode, this barrier height corresponds to a CNT film workfunction of ~4.6 eV, which is in excellent agreement with previously reported values [15,16]. As the temperature is lowered below 260oK, the weak temperature dependence of the dark current suggests that tunneling becomes the
dominant transport mechanism. In addition, we compare the dark and photocurrent of the CNT film-ba
Data Loading...
