these classes, the ZnO, GaN, 4H-SiC, 3C-SiC, and diamond are the most commonly

studied materials for applications since wearable and implantable devices to high-power

and high-temperature electronics.

Besides the electrical and optoelectronic properties, these materials also can show bio­

compatibility and biodegradability, making the WBG semiconductors convenient for ap­

plications in bioelectronics. Beyond the property of emitting short wavelengths, the wide

bandgap also results in a higher electric breakdown field, allowing applications in power

devices supported by a high breakdown field. Due to the direct bandgap in the green and

blue wavelength range, some WBG materials are suitable for optogenetic applications and

wearable UV photosensors. In the electronic context, the spontaneous and piezoelectric

polarization of WBG materials results in efficient mechanical sensors, and the high electron

mobility makes them affordable for logical circuits in biomedical applications. Several

compounds also show chemical inertness and stability due to strong covalent bonds, being

useful for long-lived recording and sensing. Additionally, these semiconductors can grow

or be transferred into flexible and biocompatible substrates, making it easier for the pre­

paration of WBG materials for wearable and implantable devices.

Understanding the structural and physical properties of WBG semiconductors is a re­

quirement to apply them in bioelectronics. In this chapter, fundamental concepts will be

presented and how the crystal structure of each family compound will define the main

properties. Different methodologies for the preparation of WBG-based materials will

change the properties of the final device. Therefore, choosing an adequate method to

prepare these materials is essential to obtain efficient devices, depending on the appli­

cation. This chapter will show diverse methodologies to grow WBG compounds and the

main applications of these materials in several bioelectronics devices.

13.2 Classes of Wide Bandgap Semiconductors

The main groups of wide bandgap semiconductors are II−VI, III−nitride, and SiC, which

have attracted the attention of several researchers for the use of these materials in bioe­

lectronics. The crystalline structure of these compounds is an important factor for de­

termining the physical properties of semiconductor materials. This section will provide

you with the general and fundamental structural properties of each material family,

which enables their implantable and wearable applications.

13.2.1 II−VI Materials

In this class of WBG semiconductors, the compounds are formed by metal from the group

IIA or IIB with a chalcogenide element (group-VI) [1], and they are widely applied in

several optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes [1,2].

The binary semiconductor compounds with bivalent metal chalcogenides (M²⁺X²⁻, where

typically M = Zn, Cd, Be, Mg, and X = O, S, Se, Te) are the simplest class of WBG

chalcogenides and the most common for electronic applications [1]. One of the most ty­

pical II−VI semiconductors is zinc oxide (ZnO), which has been largely studied for

flexible electronics due to good optical transparency, piezoelectricity, direct energy

bandgap, excellent electron mobility, and the possibility to synthesize into different na­

noarchitectures [2,3]. Another common semiconductor of this class is the CdS, which have

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Bioelectronics