Characteristics of a Pd–oxide–In0.49Ga0.51P high electron mobility transistor (HEMT)-based hydrogen sensor
Introduction
Catalytic sensing devices are widely used for detecting hydrogen gas in chemical industries, semiconductor fabrication, medical treatment and hydrogen fueled vehicles. Thus, the continuous monitoring of hydrogen gas using sensitive hydrogen sensor becomes a crucial issue. Over the past years, several material systems have been reported and used in different sensor applications [1], [2], [3], [4], [5], [6]. Due to its mature techniques, the Si-based hydrogen sensor, produced by a metal–oxide–semiconductor (MOS) structure with a catalytic metal, was first reported by Lundström et al. [7]. In order to match practical integrated circuit (IC) and micro electro-mechanical system (MEMS) applications, many different field-effect transistor (FET) structures have attracted much attention in semiconductor-type hydrogen sensor fabrication [8], [9]. However, the complicated process is a drawback of these FET devices. On the other hand, the compound semiconductors are good candidates for hydrogen detection based on the performances of high detection sensitivity, high temperature tolerance, and short response time [10], [11]. The In0.49Ga0.51P material advantages including (1) the lattice matched to GaAs, (2) the absence of DX center, (3) the small surface recombination, and (4) the high etch selectivity between InGaP and GaAs which leads to the controllable fabrication process and high-yield production in microwave, high-power, high-frequency, and opto-electronic device applications [12], [13], [14], [15], [16]. InGaP-based Schottky diode exhibits good performance of high hydrogen detection sensitivity, short response time and wide temperature operating regime [17]. However, these sensors are difficult to detect lower hydrogen concentration. In this work, a new hydrogen sensor, based on an InGaP high electron mobility transistor (HEMT) with a catalytic palladium metal–oxide–semiconductor (Pd–MOS) Schottky structure, is fabricated and studied. The hydrogen detection sensitivity is related to a change in the contact potential at the Pd/insulator interface. The studied device exhibits the advantages of high hydrogen detection sensitivity, shorter response time and wide temperature operating regime.
Section snippets
Experiments
The studied device was grown on a (1 0 0) oriented semi-insulated (SI) GaAs substrate by metal organic chemical vapor deposition (MOCVD). The device structure consisted of a 5000 Å-thick GaAs undoped buffer, a 150 Å-thick undoped In0.15Ga0.85As strained channel, a 45 Å-thick undoped Al0.24Ga0.76As spacer (electron mobility improvement), a Si planar-doped (δ(n+) = 4 × 1012 cm−2) layer (channel carrier source), a 200 Å-thick n-Al0.24Ga0.76As (n = 3 × 1017 cm−3) Schottky layer, a 30 Å-thick n-In0.24Ga0.76P (n = 3 × 10
Results and discussion
Generally, the hydrogen-sensing mechanism can be expressed by the reaction kinetics as follows [18]. Hydrogen molecules in air are dissociated on the catalytic metal surface and hydrogen atoms are adsorbed on the catalytic metal surface. Some of hydrogen atoms diffuse through the thin catalytic metal film and adsorbed on the metal–insulator interface. Hydrogen atoms adsorbed at the interface are polarized which creates a dipole layer. The polarization of the dipole layer causes an additional
Conclusion
In summary, a high-performance hydrogen sensor based on an HEMT device utilizing a Pd/oxide/In0.49Ga0.51P MOS-structure is fabricated and demonstrated. As compared with diode-type hydrogen sensors, the studied device shows good hydrogen detecting sensitivity, lower hydrogen concentration limitation and shorter response time at lower temperature regime. From the I–V analysis, the maximum detection current variation and threshold voltage shift are 3.96 mA and −127 mV, respectively, under the
Acknowledgement
Part of this work was supported by the National Science Council of the Republic of China under Contract No. NSC 92-2215-E-006-007.
Chin-Chuan Cheng was born in Chia-I, Taiwan, ROC on 26 December 1971. He received the BS and MS degrees in electrical engineering from the National Cheng-Kung University, Tainan, Taiwan, ROC in 1995 and 1997, respectively. He is currently pursuing the PhD in the electrical engineering at the National Cheng-Kung University His research interests are in the field of III–V semiconductor devices, such as HEBT- and NDR-related devices.
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Cited by (0)
Chin-Chuan Cheng was born in Chia-I, Taiwan, ROC on 26 December 1971. He received the BS and MS degrees in electrical engineering from the National Cheng-Kung University, Tainan, Taiwan, ROC in 1995 and 1997, respectively. He is currently pursuing the PhD in the electrical engineering at the National Cheng-Kung University His research interests are in the field of III–V semiconductor devices, such as HEBT- and NDR-related devices.
Yan-Ying Tsai was born in Chiayi, Taiwan, ROC on 4 January 1978. He received the BS degree in the Department of Electrical Engineering from the Sun Yat-Sen University in 2001 and the MS degree in the institute of microelectronics at the National Cheng-Kung University, Taiwan. He is currently pursuing the PhD in the Institute of Microelectronics and Department of Electrical Engineering at the National Cheng-Kung University. His research has focused on the field of III–V compound semiconductor devices and gas sensors.
Kun-Wei Lin was born in Yurn-Lin, Taiwan, ROC on 21 May 1971. He received the BS degree in electrical engineering from Fu-Jen University, Taipei, Taiwan, ROC in 1995, the MS and PhD degrees in electrical engineering from the Cheng-Kung University, Tainan, Taiwan, ROC in 1997 and 2003, respectively. He joined the faculty at Chien Kuo Institute of Technology as an instructor with the Department of Electrical Engineering in 2000. He is currently an assistant professor in the same department. His research interests are in the field of III–V semiconductor devices, such as graded field-effect transistor and heterojunction bipolar transistor, and hydrogen sensors. Dr. Lin is a member of Phi Tau Phi.
Huey-Ing Chen was born in Tainan, Taiwan, ROC in 1957. She received the BS, MS, and PhD degrees from Cheng Kung University (NCKU), Tainan, Taiwan, in 1979, 1981, and 1994, respectively, all in chemical engineering. She joined the faculty at NCKU as an instructor and an associate professor in the Department of Chemical Engineering in 1981 and 1994, respectively. She is currently an associate professor in the same department. Her research presently focuses on hydrogen permselective Pd-based membranes, hydrogen sensors, gas separations, and nanoparticles.
Wei-Hsi Hsu was born in Changhua, Taiwan, ROC on 4 March 1980. He received the BS degree in the Department of Electrical Engineering from the National Cheng-Kung University, Tainan, Taiwan, ROC in 2003. He is currently pursuing the MS degree in the Institute of Microelectronics at the National Cheng-Kung University. His research has focused on semiconductor-type hydrogen sensors.
Ching-Wen Hong was born in Koashiung, Taiwan, ROC on 15 December 1981. He received the BS degree in the Department of Electrical Engineering from the National Cheng-Kung University, Tainan, Taiwan, ROC in 2004. He is currently pursuing the MS degree in the Institute of Microelectronics at the National Cheng-Kung University. His research has focused on III–V compound semiconductor gas sensors.
Wen-Chau Liu (A′91-M′93-SM′02) was born in Yurn-Lin Hsien, Taiwan, ROC, on June 1957. He received the BSE, MSE, and PhD degrees from National Cheng-Kung University, Tainan, Taiwan, in 1979, 1981, and 1986, respectively, all in electrical engineering. He has passed the Higher Civil Service examinations and has obtained the technical expert licenses of ROC in the electrical and electronic fields in 1979 and 1982, respectively. He joined the faculty at National Cheng-Kung University as an Instructor and an Associate Professor in the Department of Electrical Engineering in 1983 and 1986, respectively. Since 1992, he has been a Professor in the same department. His research and teaching concern semiconductor device physics, analysis, and modeling. His research presently focuses on III–V heterostructure and superlattice devices including induced base transistor (IBT), superlattice-gate and heterostructure buffer layer FETs, camel structure gate FET, sawtooth-doping-superlatticed (SDS) devices, heterostructure-emitter bipolar transistor (HEBT), superlattice-emitter resonant-tunneling bipolar transistor (SE-RTBT), heterostructure-emitter and heterostructure-base transistor (HEHBT), superlatticed negative-differential-resistance (NDR) device, quantum-well δ-doped NDR devices, metal–insulator–semiconductor (MIS) like multiple switching devices, low-dimensional quantum electron devices, deep sub-micron meter devices and technologies, and high-sensitivity semiconductor gas sensors. He has published over 220 journal papers. He holds 46 patents in the semiconductor field. Dr. Liu is a member of Phi Tau Phi.