<p>Devices capable of handling high power and high frequency simultaneously are of great use in various future applications such as space, defense, and wireless power transmission. Wideband gap materials such as gallium nitride (GaN) have high electron mobility and greater thermal stability, making them a prominent candidate for these applications. In this paper, we extensively reviewed some state-of-the-art works that successfully designed and fabricated GaN-based high-frequency devices. The principal objective of this study is to highlight the pivotal factors that are responsible for hindering high-frequency applications. Moreover, we have demonstrated the novel techniques and fabrication processes adopted by the researchers to overcome these problems for enhancing the cut-off frequency (<i>f</i>_t) and the maximum frequency (<i>f</i>_max) at optimal gain (in dB) and power-added efficiency (PAE). This study also encompasses a systematic discussion on every factor that directly contributes to the high-frequency application and also portrays the current technologies available in the market, adopted by renowned foundries.</p>