Micro Humidity Sensor Based on a GaN Chip With Silica Opal

Abstract

The fabrication of a micro humidity sensor based on a GaN chip with silica opal is reported. The GaN chip containing InGaN/GaN multi-quantum well provides the two key functions of light emission and detection and the emitted light can be directly coupled into and out of the humidity-sensitive opal through the transparent sapphire substrate. The novel chip-scale integration scheme fully eliminates the complex assembly of external optical elements. The measured photocurrent signal quantitatively reflects the humidity change and has a linear relation of 0.24 µA/% over a wide humidity range of 10-90 %. The developed micro-sensor possesses the advantages of compact size, low cost, high repeatability, and ease of integration and operation, which paves the way for its widespread adoption in humidity sensing.Index Terms-Gallium nitride, optoelectronic integration, micro humidity sensor. I. INTRODUCTIONH UMIDITY is a critical parameter in numerous fields of industrial manufacturing, human activity, medical and chemical processing [1], [2]. With the rapid development of portable sensing equipment, the demand for a humidity sensor with comprehensive performances of fast response, high sensitivity, small size, and low cost, is emerging as an important trend. In addition to sensing schemes of humidity based on the variations of resistance [3], [4], capacitance [5], [6], and impedance [7], [8], optical detection via spectrum change has received increasing attention and is considered as a promising approach to meet the above criteria [9]. A variety of optically

LED with automatic brightness control utilizing the dual function of simultaneous light emission and detection

“…The existing optoelectronic integration applications include waveguides, sensors, etc. [13][14][15][16] It is worth noting that because of the overlap between its electroluminescence spectrum and spectrum responsivity (SR), that is, the light that partially overlaps with the emission spectrum band can be detected, the MQW-LED can absorb the high-energy photons from another same LED and make the carriers of the internal structure flow out, thus generating photocurrent.…”

Chip-Scale In Situ Salinity Sensing Based on a Monolithic Optoelectronic Chip

“…With the excellent inherent characteristics in response time, operating lifespan, and mechanical and chemical stability, the III-nitride semiconductor material shows considerable potential in constructing optoelectronic sensors. Recently, monolithic integration of optical and electronic components on a single GaN-based platform has been reported and applied in heart rate monitoring and refractive index, pressure, and humidity sensing . Theoretically, the refractive index is also a function of salinity, and thus, it is possible to develop GaN-based optoelectronic devices for salinity sensing.…”

“…Recently, monolithic integration of optical and electronic components on a single GaN-based platform has been reported and applied in heart rate monitoring 26 and refractive index, 27 pressure, 28 and humidity sensing. 29 Theoretically, the refractive index is also a function of salinity, 30 and thus, it is possible to develop GaNbased optoelectronic devices for salinity sensing. Noticeably, reliability problems may arise for salinity sensing based on optical means when operating under complex environmental conditions, such as cell culture medium and marine water.…”