Band bending is a central concept in solid-state physics that arises from local variations in charge distribution especially near semiconductor interfaces and surfaces [1][2][3]. Its precision measurement is vital in a variety of contexts from the optimisation of field effect transistors [4][5][6] to the engineering of qubit devices with enhanced stability and coherence [7][8][9]. Existing methods are surface sensitive and are unable to probe band bending at depth from surface or bulk charges related to crystal defects [1, 10-12]. Here we propose an in-situ method for probing band bending in a semiconductor device by imaging an array of atomic-sized quantum sensing defects to report on the local electric field. We implement the concept using the nitrogen-vacancy centre in diamond [13,14], and map the electric field at different depths under various surface terminations. We then fabricate a two-terminal device based on the conductive two-dimensional hole gas formed at a hydrogen-terminated diamond surface [15], and observe an unexpected spatial modulation of the electric field attributed to a complex interplay between charge injection and photo-ionisation effects. Our method opens the way to three-dimensional mapping of band bending in diamond and other semiconductors hosting suitable quantum sensors, combined with simultaneous imaging of charge transport in complex operating devices [16].The emergence of semiconductor-based quantum sensing technologies in the last decade has opened new opportunities in a range of disciplines across physics, materials science and biology [17]. While most existing applications involve sensors that are external to the target sample to be measured [18,19], in-situ quantum sensors can also be an extremely valuable resource to study the sample itself by enabling three-dimensional (3D) mapping [20]. For semiconductor materials this is especially advantageous as it allows information to be gained on * These authors contributed equally to this work. †

The SiC/SiO 2 interface is a central component of many SiC electronic devices. Defects intrinsic to this interface can have a profound effect on their operation and reliability. It is therefore crucial to both understand the nature of these defects and develop characterization methods to enable optimized SiCbased devices. Here we make use of confocal microscopy to address single SiC/SiO 2-related defects and show the technique to be a noncontact, nondestructive, spatially resolved and rapid means of assessing thequality of the SiC/SiO 2 interface. This is achieved by a systematic investigation of the defect density of the SiC/SiO 2 interface by varying the parameters of a nitric oxide passivation anneal after oxidation. Standard capacitance-based characterization techniques are used to benchmark optical emission rates and densities of the optically active SiC/SiO 2-related defects. Further insight into the nature of these defects is provided by low-temperature optical measurements on single defects.

Au-hyperdoped Si absorbs near-infrared (NIR) light and recent efforts have successfully produced Si-based NIR photodetectors based on this property but with low detection efficiencies. Here, we investigate the differences between the optical and photocurrent properties of Au-hyperdoped Si. Although defects introduced during fabrication of these materials may not exhibit significant optical absorption, we show that they can produce a measurable photocurrent under NIR illumination. Our results indicate that the optimal efficiency of impurity-hyperdoped Si materials is yet to be achieved and we discuss these opportunities in light of our results. This work thus represents a step forward in demonstrating the viability of using impurity-hyperdoped Si materials for NIR photodetection.