With the rapid development of technology and the expansion of the information age, self-powered systems are gradually emerging. Triboelectric nanogenerators (TENGs), coupling contact electrification and electrostatic induction, can realize continuous power supplied for small devices by converting energy. Traditional TENGs mainly used organic polymer insulators as triboelectric materials, which are limited by low current density alternating current. Recently, many different semiconductor material systems, especially gallium nitride (GaN), have been tried for better electric output performance or more application potential due to their high current density direct current, which can improve the output performance and mechanical properties of TENGs and have important application value at the forefront of portable electronic devices, Internet of things, environmental and infrastructural monitoring, medical science, security, and other fields. In this review, we summarize the latest research achievements and progress on TENGs with different semiconductor structures, including metal–semiconductor TENGs, semiconductor–semiconductor TENGs, metal–insulator–semiconductor TENGs, and liquid–semiconductor TENGs. On the basis of the current TENG theory of tribovoltaic effect, the generation mechanism and performance of each TENG was represented. Direct-current TENGs based on semiconductor structure show great promise for self-powered electronic devices.

The urgent need for renewable energy source has led to a significant interest in triboelectric nanogenerators (TENGs) as a new energy technology. In contrast to traditional polymer TENGs, semiconductor direct-current TENGs are more suitable for miniaturization and integration with electronic devices. This study proposes a friction material made of depletion mode GaN high electron mobility transistors (HEMTs), which exhibit superior properties such as high two-dimensional electron gas concentration. By sliding a titanium sheet on a depletion mode GaN-based heterostructure, we have designed a metal-semiconductor direct-current triboelectric nanogenerator that achieved voltage up to 45.5 V and a peak power density of 2.32 W/m2. This generator can be used to supply DC power to 14 LEDs in series and drive a digital watch directly. In particular, the generation of direct current is predominantly influenced by the surface states of the undoped GaN cap that produce a large number of electrons and are associated with an additional electric field in the direction of the two-dimensional electron gas created in the u-GaN/AlGaN/AlN/GaN heterostructure of depletion mode GaN-based HEMTs. This research not only introduces a nitride semiconductor material of GaN-based HEMTs for the metal-semiconductor interface friction in the DC TENGs but also elucidates the current generation mechanism of GaN-based HEMT TENGs.

Traditional surface engineering, as a means of manufacturing triboelectric nanogenerator (TENG), is complex and expensive. The yield of traditional polymer process is low, which leads to the high cost and low stability of traditional TENGs and greatly limits their practical applications. Moreover, it is worth noting that with the miniaturization and integration of electronic devices, generators need to provide higher current in parallel circuits. In this study, we report the performance of the enhanced Cu/P-type GaN TENG contacts in centimeter scale. Considering the high surface mechanical strength and surface structure characteristics of GaN wafers, we propose using molten KOH to etch the Ga polar GaN surface to form more interface electrons and dangling bonds without destroying the surface structure. Our experimental results show that the generator performance has been drastically improved (the short circuit current increases from 9 to 80 μA, and the open circuit voltage increases from 8 to 29 V). The maximum load electric power density of ∼0.28 W/m2 was obtained. We also compared the open circuit current density with the reported different type TENGs based on Schottky contact at the centimeter-level. The Cu/P-type GaN TENGs achieved in this work exhibit excellent open circuit current density of ∼36 μA/cm2. Thus, we provide insight into surface engineering for future generation TENG devices.