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GaN has been considered as a promising candidate for biosensing due to its chemical and thermal stability. In this work, an AlGaN/GaN high electron mobility transistor (HEMT) wafer with a 2DEG mobility of 1300 cm2/v-s and a sheet carrier density of 1x1013 cm-2 was used as a sensor platform. Ti/Al/Ni/Au were used as source and drain contacts, with Ni/Au contacts as gate electrodes. A NF3 plasma was used for device isolation. Photodefinable PDMS was used for the purpose of encapsulation. Once the encapsulation was completed using the photodefinable PDMS, the Schottky contact was exposed to a thiolated DNA in immobilization buffer for a period of 12hours. XPS was used to confirm the probe immobilization. The change in the (Id-Vds) characteristics of the device is measured during these processes, which confirm the probe immobilization and also the probe and the target DNA hybridization.