Hybrid graphene/unintentionally doped GaN ultraviolet photodetector with high responsivity and speed

Abstract

Ultraviolet (UV) photodetectors with high responsivity and speed are highly desirable for imaging and remote sensing applications. Limited by the crystalline quality of a GaN-based material, which is ideal for UV photodetection, the further improvement of the performance is minimal. A hybrid graphene/unintentionally doped (UID) GaN UV photodetector with both high responsivity and high speed is reported. Holes in graphene, which are induced by the photogenerated electrons trapped at the graphene/UID GaN interface according to the capacitive effect, have a long lifetime owing to the electron-hole pair separation in space. Graphene acts as a carrier transport channel and greatly increases the charge collection efficiency under an external bias voltage. The responsivity of a hybrid graphene/UID GaN photodetector with a photosensitive area of 2 mm2 reaches 5.83 A/W at −10 V with a specific detectivity of ∼1011 Jones. The response time is ∼5 ms, which is faster than that of traditional GaN photodetectors. These results will provide a feasible route to UV detection with high performance.

Role of ZrO2 Passivation Layer Thickness in the Fabrication of High‐Responsivity GaN Ultraviolet Photodetectors

“…Under such circumstances, a viable solution for enhancing D * can be obtained by maximizing the value of responsivity via a controlled passivation of surface states in the GaN layer, as shown in Figure a. In Figure b, recently reported values of D * for several state‐of‐the‐art visible blind GaN UV PDs are plotted as a function of dark current along with our results. Note that the value of D * measured for sample B is higher or comparable to the values reported in the literature irrespective of its large dark current.…”

“…Another important figure of merit of PDs is the specific detectivity ( D *), which corresponds to their ability to detect the weakest signal. Recently, a few methods have been proposed by researchers for enhancing the value of D *, which is actually estimated by following the procedure given by Gong et al. To compare the values of D * of our devices with the recently reported state‐of‐the‐art values, we also followed the same procedure, and the estimated values of D * are plotted in Figure a.…”

High responsivity and high speed InGaN-based blue-light photodetectors on Si substrates

“…The D* of sample 1 based blue-light PDs is signicantly higher than that of sample 2 based blue-light PDs thanks to the higher crystalline quality of InGaN in sample 1 that leads to the lower I dark . 24,25 To measure the response speed of the fabricated blue-light PDs, the time response of the photo-current for rise time and fall time of the sample 1 based and sample 2 based blue-light PDs was carried out as shown in Fig. 4(b, c) and (e, f), respectively.…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…21(a). Their reported device characteristic values were significantly higher than those realized without the integration of graphene layers (up to 700-fold improvement); the high achieved gain can be attributed to high carrier mobility effects exhibited in graphene, which allow for multiple carrier transport to generate high photocurrent densities [552] . Without the graphene layer, it can be expected that generated carriers would be trapped in the lower-mobility GaN layer, limiting the achievable photocurrents and gains in PD devices.…”