Review—Semiconductor Materials and Devices for Gas Sensors

Abstract

Gas sensors are frequently used for detecting toxic gases and vapors for environmental control, industrial monitoring, and household safety. Semiconductor conductivity can be modified by doping or fine-tuned by applying an electric or magnetic field in an ultra-wide range (10-7 S/cm to 102 S/cm). The conduction of semiconductor is significantly raised or reduced upon the exposure to external conditions, such as temperature variation, light, heat, mechanical stress, or chemicals. Thus, semiconductors are excellent materials for sensors and the device structures are critical for sensing performance. The commonly used semiconductors materials include Si, Ge, III-V, and metal oxide semiconductors. Recently carbon-based materials gain signification attention due to their unique electrical, optical and mechanical properties. There are two major semiconductor gas sensors: resistor-based and FET-based sensors. In this review, the semiconductor materials, sensor device structure as well as gas sensing mechanisms will be systematically categorized, described and explored, with the focus on metal oxides, GaN, SiC, 2D-TMD and carbon-based gas sensors. The recent progress in new semiconductor gas sensors will be thoroughly reviewed and summarized, with a hope to show the trend in semiconductor gas sensor technology.

Environmental gas sensors based on electroactive hybrid organic–inorganic nanocomposites using nanostructured materials

“…The mechanism is different for different types of semiconductors, such as N-type, P-type, heterojunction, etc. 55 This difference is illustrated in detail here.…”

“…Pollutants are various hazardous substances present in the air that damage our environment, causing severe harm to the health of all living organisms. [53][54][55] Such hazardous contaminants are released into the atmosphere from the products of chemical reactions/ combustion, leakage of harmful industrial wastes and gases, and the intentional discharge of chemical warfare agents. It is a severe environmental problem of worldwide concern.…”

“…The combination of two different types of semiconductor materials forms a heterojunction. 55 When an n-type semiconductor is combined with a p-type semiconductor, a hetero-heterojunction is formed. Again, incorporating the same type of semiconductor materials, such as p-type with p-type or n-type with n-type, leads to the formation of homogeneous heterojunctions.…”

“…This type of hybrid sensor is formed by combining two different types of semiconductor materials. 55 Here, the electrons flow from a higher energy state to a lower energy state, while the holes flow from a lower to a higher energy state until the Fermi level attains the equilibrium state. The heterojunction type decides whether a depletion or an accumulation layer is formed.…”

First-Principles Investigation of Adsorption Behaviors and Electronic, Optical, and Gas-Sensing Properties of Pure and Pd-Decorated GeS2 Monolayers

“…Since gas sensors have widely penetrated every aspect of our daily lives, such as medical and food industries and environmental safety testing, − 2D TMDs are ideal gas sensing materials due to their large specific surface-to-volume ratios, high sensitivity to adsorption of gases, which are available for interactions with gas molecules, abundant active sites to selectively bind gases, and good mechanical properties. − As one of the most common air pollutants, NO x ( x = 1 and 2), which are mainly from the combustion of fossil fuels, are greatly harmful to the environment and human health such as the damage of human respiratory organs and nerves. , Therefore, the development and manufacture of highly sensitive and selective NO x gas sensors is a main challenge for monitoring air quality, especially, for the detection of NO x at parts per billion (ppb) levels for commercial applications in environmental monitoring and healthcare.…”