Electron beam techniques have been used to analyze the impact of substrate choice and growth parameters on the compositional and optical properties of tin gallium oxide [(SnxGa1−x)2O3] thin films grown by plasma‐assisted molecular beam epitaxy. Sn incorporation and film quality are found to be highly dependent on growth temperature and substrate material (silicon, sapphire, and bulk Ga2O3) with alloy concentrations varying up to an x value of 0.11. Room temperature cathodoluminescence spectra show the Sn alloying suppressing UV (3.3–3.0 eV), enhancing blue (2.8–2.4 eV), and generating green (2.4–2.0 eV) emission, indicative of the introduction of a high density of gallium vacancies (VGa) and subsequent VGa–Sn complexes. This behavior was further analyzed by mapping composition and luminescence across a cross section. Compared to Ga2O3, the spectral bands show a clear redshift due to bandgap reduction, confirmed by optical transmission measurements. The results show promise that the bandgap of gallium oxide can successfully be reduced through Sn alloying and used for bandgap engineering within UV optoelectronic devices.

Tin-gallium oxide (TGO) epilayers have been characterized through the electron microscopy techniques of wavelength-dispersive X-ray spectroscopy (WDX) and cathodoluminescence. Tin incorporation was found to be highly dependent on growth conditions with (0001)-sapphire and (010)-Ga2O3 substrates enhancing tin incorporation. Cathodoluminescence measurements show that TGO luminescence consists of an enhanced blue emission and quenched UV when compared to Ga2O3.and the onset of new green emission originating from the TGO, further correlated through cross-sectional WDX and cathodoluminescence mapping. As well as luminescence intensity changes TGO films display redshifted luminescence bands associated with a bandgap reduction due to the alloying, confirmed through optical transmission measurements.

We report ultra-high responsivity of epitaxial (SnxGa1−x)2O3 (TGO) Schottky UV-C photodetectors and experimentally identified the source of gain as deep-level defects, supported by first principles calculations. Epitaxial TGO films were grown by plasma-assisted molecular beam epitaxy on (−201) oriented n-type β-Ga2O3 substrates. Fabricated vertical Schottky devices exhibited peak responsivities as high as 3.5 ×104 A/W at −5 V applied bias under 250 nm illumination with sharp cutoff shorter than 280 nm and fast rise/fall time in milliseconds order. Hyperspectral imaging cathodoluminescence (CL) spectra were examined to find the mid-bandgap defects, the source of this high gain. Irrespective of different tin mole fractions, the TGO epilayer exhibited extra CL peaks at the green band (∼2.20 eV) not seen in β-Ga2O3 along with enhancement of the blue emission-band (∼2.64 eV) and suppression of the UV emission-band. Based on hybrid functional calculations of the optical emission expected for defects involving Sn in β-Ga2O3, VGa–Sn complexes are proposed as potential defect origins of the observed green and blue emission-bands. Such complexes behave as acceptors that can efficiently trap photogenerated holes and are predicted to be predominantly responsible for the ultra-high photoconductive gain in the Sn-alloyed Ga2O3 devices by means of thermionic emission and electron tunneling. Regenerating the VGa–Sn defect complexes by optimizing the growth techniques, we have demonstrated a planar Schottky UV-C photodetector of the highest peak responsivity.

A high figure‐of‐merit UV‐C solar‐blind photodetector (PD) fabricated from thin‐film beta‐gallium oxide (β‐Ga2O3) grown on n‐Si substrates by plasma‐assisted molecular beam epitaxy is demonstrated. Film growth sequences for nucleation of Ga2O3 on (100)‐ and (111)‐oriented Si substrates are developed, and the influence of crucial growth parameters is systematically investigated, namely, substrate temperature, oxygen flow rate, and plasma power on the functional properties of the PDs. The PDs show an ultra‐high responsivity of 837 A W−1 and a fast ON/OFF time below 4 ms at −5 V. In addition, they display strong rectifying properties and a sharp cutoff below 280 nm with the average responsivities between 10 and 80 A W−1, a detectivity on the order of 1010 Jones, and rise/fall times between 4 and 500 ms. High photoconductive gain is likely to be due to the mid‐bandgap donor/acceptor defect levels, including oxygen vacancies in the form of self‐trapped holes. It is demonstrated that these defect levels can be modified by controlling the growth conditions, thereby allowing for tailoring of the PD characteristics for specific applications. The methodology represents a cost‐effective solution over homoepitaxial approaches, with characteristics that meet or exceed those reported previously, offering new possibilities for on‐wafer integration with Si opto‐electronics.

Heterogeneous integration of β-(SnxGa1−x)2O3 (TGO) UV-C photodetectors on silicon substrates by molecular beam epitaxy is demonstrated. Multimodal electron microscopy and spectroscopy techniques reveal a direct correlation between structural, compositional, and optical properties of TGO and the functional properties of the photodetectors. Wavelength dispersive x-ray spectroscopy results accurately determine Sn concentrations (x) in the region of 0.020, and room temperature cathodoluminescence (CL) hyperspectral imaging shows changes in the CL emission intensity in TGO compared with a Ga2O3 sample with no Sn. Alloying Ga2O3 with Sn is shown to quench the red emission and enhance the blue emission. The increase in blue emission corresponds to the rise in VGa-related deep acceptors responsible for the high gain observed in the TGO detectors. A Ga2O3 nucleation layer is shown to improve the TGO surface quality and give better device properties compared to TGO grown directly onto the Si substrate, including a higher specific detectivity on the order of 1012 Jones.

We report on the fabrication and characterization of solar-blind photodetectors based on metal organic chemical vapor deposition grown polycrystalline monoclinic indium gallium oxide (InxGa1-x)(2)O-3 alloys on sapphire using N2O for oxidation. The effects of growth conditions on indium incorporation efficiency and oxygen vacancies of the (InxGa1-x)(2)O-3 alloy, photo-to-dark current ratio (PDR), gain and responsivity of the fabricated photodetectors were investigated. The optical bandgap of the films was found to decrease due to the indium incorporation (x = 20.3%, 17.7%, 10.6% for samples A, B, and C, respectively) into the lattice of gallium oxide. By increasing the indium content incorporated into the lattice of Ga2O3, we demonstrated solar-blind photodetectors whose peak responsivity increased from 0.79 A/W (Ga2O3) to 319.1 A/W, 66.1 A/W and 27.7 A/W for samples A, B and C, respectively at 5 V applied bias with the cut off wavelength below 280 nm. Increasing in content resulted in a higher concentration of oxygen vacancies in as-grown films. Increased oxygen vacancies as a result of the change in growth conditions lead to higher photoconductive gain, higher responsivities, and lower PDR, demonstrating a trade-off between responsivity and the PDR. To the best of our knowledge, the peak responsivity value reported in this work is the highest for (InxGa1-x)(2)O-3 based solar-blind photodetectors. Fast rise and fall times in the order of 100 ms have been measured for the photodetectors.

Range imaging plays an essential role in many fields: 3D modeling, robotics, heritage, agriculture, forestry, reverse engineering. One of the most popular range-measuring technologies is laser scanner due to its several advantages: long range, high precision, real-time measurement capabilities, and no dependence on lighting conditions. However, laser scanners are very costly. Their high cost prevents widespread use in applications. Due to the latest developments in technology, now, low-cost, reliable, faster, and light-weight 1D laser range finders (LRFs) are available. A low-cost 1D LRF with a scanning mechanism, providing the ability of laser beam steering for additional dimensions, enables to capture a depth map. In this work, we present an unsynchronized scanning with a low-cost LRF to decrease scanning period and reduce vibrations caused by stop-scan in synchronized scanning. Moreover, we developed an algorithm for alignment of unsynchronized raw data and proposed range image post-processing framework. The proposed technique enables to have a range imaging system for a fraction of the price of its counterparts. The results prove that the proposed method can fulfill the need for a low-cost laser scanning for range imaging for static environments because the most significant limitation of the method is the scanning period which is about 2 minutes for 55,000 range points (resolution of 250x220 image). In contrast, scanning the same image takes around 4 minutes in synchronized scanning. Once faster, longer range, and narrow beam LRFs are available, the methods proposed in this work can produce better results.