Humidity Sensor of p-n InN/Si Nanostructure With GHz Resonant Microwave Property

• Published in: IEEE sensors journal 2015-10, Vol.15 (10), p.5938-5945
• Main Authors: Yang, Chih Chin, Wang, Jing Yi
• Format: Article
• Language: English
• Subjects: Annealing; Buffer layers; Humidity; Indium; microwave; resistance; resonant; sensor; Sensors; Silicon
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2015.2449873

As the growth temperature, annealing temperature, and annealing time of InN sensing film of InN/InNO/In 2 O 3 /In/SiO 2 /Si humidity sensor were, respectively, adjusted at 400°C, 400°C, and 15 min, the sensing surface possesses obvious particles of nanometer scale. The particle size of InN sensing film was estimated about 65 nm which realized the quantum effect of InN sensing film for the humidity sensing performance in chemistry. The designed p-n InN/InNO/In 2 O 3 /In/SiO 2 /Si structures of humidity sensor in this paper contained three different buffer layers (indium layer, InNO layer, and In 2 O 3 layer) which also revealed the negative differential resistance effect with peak current density of 2.8 kA/cm 2 and peak-to-valley current ratio of 1.93 for quantum resonant microwave performance in physics. The periods of water molecular adsorption and desorption are ~600 and 580 s, respectively. The sensing resolution of adsorption and desorption is defined by resistance variation per second. The response sensitivity (SR) of adsorption and desorption are ~0.25 mQ/s (0.1%RH/s) and 0.41 mQ/s (0.1%RH/s), respectively. The InN/InNO/In 2 O 3 /In/SiO 2 /Si humidity sensor revealed the sensing sensitivity of 6 × 10 -3 ohm/% RH. The InN/InNO/In 2 O 3 /In/SiO 2 /Si humidity sensor also revealed the resistive cutoff frequency ( fr) and the selfresonant frequency (fSR) of microwave device reached as 1.6 MHz and 70 GHz, respectively. Microwave transmission property of p-n InN/InNO/In 2 O 3 /In/SiO 2 /Si humidity sensor reached as gigahertz frequency range can transfer the humidity signal from patient to monitoring station via high frequency wireless communication from one device. InN/InNO/In 2 O 3 /In/SiO 2 /Si humidity sensor can be, therefore, applied in wireless microwave transmission of human body sensing signal.