An official website of the United States government
Polarization-induced two-dimensional electron gases (2DEGs) in AlN/GaN/AlN quantum well high-electron-mobility transistors on ultrawide bandgap AlN substrates offer a promising route to advance microwave and power electronics with nitride semiconductors. The electron mobility in thin GaN quantum wells embedded in AlN is limited by high internal electric field and the presence of undesired polarization-induced two-dimensional hole gases (2DHGs). To enhance the electron mobility in such heterostructures on AlN, previous efforts have resorted to thick, relaxed GaN channels with dislocations. In this work, we introduce n-type compensation δ-doping in a coherently strained single-crystal (Xtal) AlN/GaN/AlN heterostructure to counter the 2DHG formation at the GaN/AlN interface, and simultaneously lower the internal electric field in the well. This approach yields a δ-doped XHEMT structure with a high 2DEG density of ∼3.2×1013 cm−2 and a room temperature (RT) mobility of ∼855 cm2/Vs, resulting in the lowest RT sheet resistance 226.7 Ω/□ reported to date in coherently strained AlN/GaN/AlN HEMT heterostructures on the AlN platform.
more »
« less
Molecular Beam Epitaxy Growth of Large‐Area GaN/AlN 2D Hole Gas Heterostructures
Large‐area growth of polarization‐induced 2D hole gases (2DHGs) in a GaN/AlN heterostructure using molecular beam epitaxy (MBE) is demonstrated. A study of the effect of metal fluxes and substrate temperature during growth is conducted to optimize the 2DHG transport. These conditions are adopted for the growth on 2 in. wafer substrates. The obtained results represent a step forward towards achieving a GaN/AlN 2DHG platform for high‐performance wide‐bandgap p‐channel field effect transistors (FETs).
more »
« less
- Award ID(s):
- 1719875
- PAR ID:
- 10130848
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- physica status solidi (b)
- Volume:
- 257
- Issue:
- 4
- ISSN:
- 0370-1972
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract High hole densities are desired in p‐channel field effect transistors to improve the speed and on‐currents. Building on the recently discovered undoped, polarization‐induced GaN/AlN 2D hole gas (2DHG), this work demonstrates the tuning of the piezoelectric polarization difference across the heterointerface by introducing indium in the GaN channel. Using careful design and epitaxial growths, these pseudomorphic (In)GaN/AlN heterostructures result in some of the highest carrier densities of >1014cm−2in a III‐nitride heterostructure—just an order below the intrinsic crystal limit of ≈1015cm−2. These ultra‐high density InGaN/AlN 2DHGs show room temperature mobilities of 0.5–4 cm2V−1s−1and do not freeze out at low temperatures. A characteristic alloy fluctuation energy of 1.0 eV for hole scattering in InGaN alloy is proposed based on the experiments.more » « less
-
The recent demonstration of W mm−1output power at 94 GHz in AlN/GaN/AlN high‐electron‐mobility transistors (HEMTs) has established AlN as a promising platform for millimeter‐wave electronics. The current state‐of‐art AlN HEMTs using ex situ‐deposited silicon nitride (SiN) passivation layers suffer from soft gain compression due to trapping of carriers by surface states. Reducing surface state dispersion in these devices is thus desired to access higher output powers. Herein, a potential solution using a novel in situ crystalline AlN passivation layer is provided. A thick, 30+ nm‐top AlN passivation layer moves the as‐grown surface away from the 2D electron gas (2DEG) channel and reduces its effect on the device. Through a series of metal‐polar AlN/GaN/AlN heterostructure growths, it is found that pseudomorphically strained 15 nm thin GaN channels are crucial to be able to grow thick AlN barriers without cracking. The fabricated recessed‐gate HEMTs on an optimized heterostructure with 50 nm AlN barrier layer and 15 nm GaN channel layer show reduction in dispersion down to compared with in current state‐of‐art ex situ SiN‐passivated HEMTs. These results demonstrate the efficacy of this unique in situ crystalline AlN passivation technique and should unlock higher mm‐wave powers in next‐generation AlN HEMTs.more » « less
-
Abstract Gallium nitride high-electron-mobility transistors (GaN HEMTs) are at a point of rapid growth in defense (radar, SATCOM) and commercial (5G and beyond) industries. This growth also comes at a point at which the standard GaN heterostructures remain unoptimized for maximum performance. For this reason, we propose the shift to the aluminum nitride (AlN) platform. AlN allows for smarter, highly-scaled heterostructure design that will improve the output power and thermal management of III-nitride amplifiers. Beyond improvements over the incumbent amplifier technology, AlN will allow for a level of integration previously unachievable with GaN electronics. State-of-the-art high-current p-channel FETs, mature filter technology, and advanced waveguides, all monolithically integrated with an AlN/GaN/AlN HEMT, is made possible with AlN. It is on this new AlN platform that nitride electronics may maximize their full high-power, high-speed potential for mm-wave communication and high-power logic applications.more » « less
-
Aluminum nitride (AlN) offers novel potential for electronic integration and performance benefits for high‐power, millimeter‐wave amplification. Herein, load‐pull power performance at 30 and 94 GHz for AlN/GaN/AlN high‐electron‐mobility transistors (HEMTs) on silicon carbide (SiC) is reported. When tuned for peak power‐added efficiency (PAE), the reported AlN/GaN/AlN HEMT shows PAE of 25% and 15%, with associated output power () of 2.5 and 1.7 W mm−1, at 30 and 94 GHz, respectively. At 94 GHz, the maximum generated is 2.2 W mm−1, with associated PAE of 13%.more » « less
