High Figure‐of‐Merit Gallium Oxide UV Photodetector on Silicon by Molecular Beam Epitaxy: A Path toward Monolithic Integration

Abstract

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.

Correlation between deep-level defects and functional properties of β-(SnxGa1-x)2O3 on Si photodetectors

“…The last cleaning step was a Ga treatment as described elsewhere 24 . Prior to supplying oxygen to the MBE chamber, a Ga (Ga and Sn for sample B) pre-deposition for 10 minutes is performed at 500 °C to prevent SiO2 formation before starting to grow the nucleation layer 23 . For Sample A, a low temperature (500°C) nucleation layer of Ga2O3 was grown first (growth time 5 minutes, oxygen flow rate of 1.6 sccm, and plasma power of 300 W).…”

“…However, the use of silicon as a substrate offers several key advantages, such as cost and the enabling of monolithic integration with silicon electronics and photonics. 23 Here, we demonstrate for the first time the feasibility of producing TGO on Si substrates by molecular beam epitaxy (MBE) and correlate the devices' structural, optical and functional properties using multimode electron microscopy and spectroscopy methods. We study the effects of a Ga2O3 buffer layer beneath the TGO thin film.…”

Recent progress on the effects of impurities and defects on the properties of Ga2O3

“…The strongest peaks with binding energies of 531.6-531.9 eV were assigned to lattice oxygen (i.e., Ga-O bond), and the peaks with the highest binding energy around 532 eV were assigned to oxygen vacancy (V O ) in general. [157][158][159][160][161][162][163][164][165][166][167] The as-grown Ga 2 O 3 films were postannealed in the O 2 and N 2 atmospheres respectively in Lee et al's research. The O content increased more in the O 2 environment (O/Ga = 1.43) than in the N 2 environment (O/Ga = 1.42).…”

Regulation of oxygen vacancies in nitrogen-doped Ga2O3 films for high-performance MSM solar-blind UV photodetectors

“…The selection of suitable methods is of critical importance to improve the performance of Ga 2 O 3 films. Until now, the Ga 2 O 3 films have been grown by molecular beam epitaxy (MBE), 26,27 pulsed laser deposition (PLD), 28,29 radio frequency magnetron sputtering (RFMS), [30][31][32][33] metal organic chemical vapor deposition (MOCVD), 16,34 and mist-chemical vapor deposition (Mist-CVD). 3,14 Among all the methods, radio frequency magnetron sputtering has some advantages, such as low cost of equipment, strong film adhesion, high deposition rates, easy control of substrate temperature, superior process reproducibility and especially uniformity of ceramic target composition.…”