An official website of the United States government
This study presents the growth and characterization of an 8.1 μm-emitting, InGaAs/AlInAs/InP-based quantum cascade laser (QCL) formed on an InP-on-Si composite template by metalorganic chemical vapor deposition (MOCVD). First, for the composite-template formation, a GaAs buffer layer was grown by solid-source molecular-beam epitaxy on a commercial (001) GaP/Si substrate, thus forming a GaAs/GaP/Si template. Next, an InP metamorphic buffer layer (MBL) structure was grown atop the GaAs/GaP/Si template by MOCVD, followed by the MOCVD growth of the full QCL structure. The top-surface morphology of the GaAs/GaP/Si template before and after the InP MBL growth was assessed via atomic force microscopy, over a 100 μm2 area, and no antiphase domains were found. The average threading dislocation density (TDD) for the GaAs/GaP/Si template was found to be ∼1 × 109 cm−2, with a slightly lower defect density of ∼7.9 × 108 cm−2 after the InP MBL growth. The lasing performance of the QCL structure grown on Si was compared to that of its counterpart grown on InP native substrate and found to be quite similar. That is, the threshold-current density of the QCL on Si, for deep-etched ridge-guide devices with uncoated facets, is somewhat lower than that for its counterpart on native InP substrate, 1.50 vs 1.92 kA/cm2, while the maximum output power per facet is 1.64 vs 1.47 W. These results further demonstrate the resilience of QCLs to relatively high residual TDD values.
more »
« less
This content will become publicly available on December 1, 2026
Investigation of MOCVD Growth and Process Conditions on the Efficacy of a Simplified GaAs‐on‐Si Virtual Substrate Approach
The efficacy of metal‐organic chemical vapor deposition (MOCVD)‐based growth for the production of GaAs‐on‐Si virtual substrates following a recently reported process combining low‐temperature growth, thermal cyclic annealing (TCA), and an asymmetric step‐graded filter (ASG) structure is investigated. The impact of multiple process variables—substrate offcut, V/III molecular flux ratio, growth rate, and growth and annealing temperatures—with respect to resultant surface roughness (Rq) and threading dislocation density (TDD) is examined. Similar trends as those reported for the original molecular beam epitaxy‐based process are observed inRqand TDD for growths on both 2° and 6° offcut substrates. MOCVD process conditions are established for a reduced‐thickness design yielding GaAs virtual substrates on 2° and 6° offcut Si with TDD (≤4.0 × 106 cm−2) andRq(2.4 and 5.3 nm, respectively), comparable to conventional graded buffers, but with a total III–V thickness of less than 2.0 µm.
more »
« less
- Award ID(s):
- 2047308
- PAR ID:
- 10650998
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- physica status solidi (a)
- ISSN:
- 1862-6300
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
A new record‐high room‐temperature electron Hall mobility (μRT = 194 cm2 V−1 s−1atn ≈ 8 × 1015 cm−3) for β‐Ga2O3is demonstrated in the unintentionally doped thin film grown on (010) semi‐insulating substrate via metal‐organic chemical vapor deposition (MOCVD). A peak electron mobility of ≈9500 cm2 V−1 s−1is achieved at 45 K. Further investigation on the transport properties indicates the existence of sheet charges near the epilayer/substrate interface. Si is identified as the primary contributor to the background carrier in both the epilayer and the interface, originating from both surface contamination and growth environment. The pregrowth hydrofluoric acid cleaning of the substrate leads to an obvious decrease in Si impurity both at the interface and in the epilayer. In addition, the effect of the MOCVD growth condition, particularly the chamber pressure, on the Si impurity incorporation is studied. A positive correlation between the background charge concentration and the MOCVD growth pressure is confirmed. It is noteworthy that in a β‐Ga2O3film with very low bulk charge concentration, even a reduced sheet charge density plays an important role in the charge transport properties.more » « less
-
Thin Si-doped Al-rich (xAl > 0.85) regrown Al(Ga)N layers were deposited on AlN on sapphire template using metal-organic chemical vapor deposition (MOCVD) techniques. The optimization of the deposition conditions, such as temperature (1150 °C), V/III ratio (750), deposition rate (0.7 Å/s), and Si concentration (6 × 10^19/cm3), resulted in a high charge carrier concentration (> 10^15 cm−3) in the Si-doped Al-rich Al(Ga)N films. A pulsed deposition condition with pulsed triethylgallium and a continuous flow of trimethylaluminum and ammonia was employed to achieve a controllable Al composition xAl > 0.95 and to prevent unintended Ga incorporation in the AlGaN material deposited using the close-coupled showerhead reactor. Also, the effect of unintentional Si incorporation on free charge carrier concentration at the regrowth interface was studied by varying the thickness of the regrown Al(Ga)N layer from 65 to < 300 nm. A maximum charge carrier concentration of 4.8 × 10^16 and 7.5 × 10^15/cm3 was achieved for Al0.97Ga0.03N and AlN films with thickness <300 nm compared to previously reported n-Al(Ga)N films with thickness ≥400 nm deposited using MOCVD technique.more » « less
-
We report on the growth of Si-doped homoepitaxial β-Ga2O3 thin films on (010) Ga2O3 substrates via metal-organic chemical vapor deposition (MOCVD) utilizing triethylgallium (TEGa) and trimethylgallium (TMGa) precursors. The epitaxial growth achieved an impressive 9.5 μm thickness at 3 μm/h using TMGa, a significant advance in material growth for electronic device fabrication. This paper systematically studies the Schottky barrier diodes fabricated on the three MOCVD-grown films, each exhibiting variations in the epilayer thickness, doping levels, and growth rates. The diode from the 2 μm thick Ga2O3 epilayer with TEGa precursor demonstrates promising forward current densities, the lowest specific on-resistance, and the lowest ideality factor, endorsing TEGa’s potential for MOCVD growth. Conversely, the diode from the 9.5 μm thick Ga2O3 layer with TMGa precursor exhibits excellent characteristics in terms of lowest leakage current, highest on-off ratio, and highest reverse breakdown voltage of −510 V without any electric field management, emphasizing TMGa’s suitability for achieving high growth rates in Ga2O3 epilayers for vertical power electronic devices.more » « less
-
Abstract Herein, the first report on the isolated and unambiguously proven benzene radical trianion is presented. This unprecedented radical oxidation state of benzene is stabilized through two trivalent rare earth (RE) metal cations each supported by a bis(guanidinate) scaffold. Specifically, the one‐electron chemical reduction of the neutral inverse‐sandwich yttrium complex [[{(Me3Si)2NC(NiPr)2}2Y]2(μ–ƞ6:ƞ6–C6H6)]1, containing a benzene dianion, with potassium graphite (KC8) in the presence of [2.2.2]‐cryptand yielded the title complex [K([2.2.2]‐cryptand)][[{(Me3Si)2NC(NiPr)2}2Y]2(μ–ƞ6:ƞ6–C6H6•)]2, featuring a benzene radical trianion. Analyses through single‐crystal X‐ray diffraction, EPR and UV–vis spectroscopy, elucidated its molecular structure and revealed strong [YIII–(C6H6)3–•–YIII] metal–radical interactions. Although the Y centers remain in the +3 oxidation state, the spin density of the unpaired electron resides primarily on the benzene trianion moiety and extends toward the YIIIions. Density functional theory (DFT) calculations on2corroborate this assignment and further suggest weak aromaticity for the benzene radical trianion.more » « less
