Search

Co-integration of the key power stage, namely gate drivers and half-bridge in a single-die solution, is a tremendous and inevitable challenge to realizing GaN power integrated circuits (GaN power ICs). In this letter, a monolithically integrated GaN half-bridge including the drivers were successfully fabricated on 200-mm engineered substrates of Qromis substrate technology (QST®). Deep trench isolation together with the buried oxide of the GaN-on-QST® isolates the high side, low side, and the drivers. While on GaN-on-Si, the back-gating effect more and more impedes the integration of a half-bridge’s low side and high side as the voltage increases. This effect is fully eliminated using the proposed effective isolation strategy. In this letter, we will present a single-die GaN power IC exhibiting 200-V swift switching capability. Finally, based on this GaN power IC, a 48V-to-1V single-stage buck converter was successfully demonstrated.

In recent years, GaN has become a forefront wide bandgap semiconductor material for next-generation, energy-efficient power electronics. With its higher breakdown strength, faster switching speed and lower on-resistance, GaN power devices can convert power far more efficiently than Si-based devices. While its performance is commercially demonstrated, widespread GaN adoption requires a scalable and high-yielding manufacturable technology platform enabling economies of scale and a full spectrum of low-cost products such as lateral and vertical power switches extending from 100V to 1,200V and beyond, monolithic ICs and rectifiers. QROMIS’ disruptive commercial solution to high volume, low cost and scalable GaN device manufacturing has been steadily gaining traction, owing to unique properties of specially-designed CMOS fab-friendly and semi-spec substrate called “QST®” (QROMIS Substrate Technology) with a core having a thermal expansion that very closely matches the thermal expansion of the GaN/AlGaN epitaxial layers. QST® enables breakage-free high-volume manufacturing of standard semi-spec thickness 200mm GaN device wafers (scalable to 300mm), covering all GaN applications including 100V-to-1800V high performance power devices, RF devices, and display microLEDs. In this talk, the following status updates on 200mm QST®-based materials and device technologies will be presented: (1) commercial QST® substrate products, (2) commercial GaN-on-QST® epi-wafer products, including development studies on epi-wafers for 1,200V and beyond applications, (3) high-performance normally-off 650V p-GaN based GaN-on-QST® HEMT transistors & monolithic ICs (with integrated drivers and logic) fabricated in a CMOS fab and commercialization timelines, (4) 200mm GaN-on-QST® device foundry services for the industry players, and (5) initial high-performance GaN-on-QST® RF device results.

Lateral GaN-based p-n junction gated field effect transistor (LJFET) devices have been demonstrated on 200mm engineered substrates. The maximum current density was 200 mA/mm and threshold voltage was −30V. Large gate width devices (40mm) exhibited 800 mA current. The devices have blocking capability exceeding 1.1 kV.

We use high pressure techniques to investigate the properties of two classes of "dilute-nitride-phosphide"-based devices; GaNP/GaP light emitting diodes for yellow-amber-red display applications and GaNAsP/GaP lasers, a potential route to producing lasers monolithically on silicon. Based upon high pressure electroluminescence measurements we find that the band anti-crossing (BAC) model reasonably describes the GaN(As)P system based on an average of the nitrogen states. In terms of device characteristics, we find that carrier leakage into the X-minima of GaP reduces the efficiency of GaNP/ GaP LEDs with increasing pressure. Lasing has been observed in GaNAsP/GaP devices with a pulsed threshold current density of 2.5 kA/cm 2 at 80 K (λ = 890 nm). A weak increase in threshold current with hydrostatic pressure indicates that a carrier leakage path that does not involve the GaP X-minima is the dominant carrier recombination mechanism in these devices, in contrast to the LEDs.

AlGaN/GaN high-electron-mobility transistor (HEMT) device layers were grown by metal organic chemical vapor deposition (MOCVD) on commercial engineered QST™ substrates to demonstrate a path to scalable, cost-effective foundry processing while supporting the thick epitaxial layers required for power HEMT structures. HEMT structures on 150 mm Si substrates were also evaluated. The HEMTs on engineered substrates exhibited material quality, DC performance, and forward blocking performance superior to those of the HEMT on Si. GaN device layers up to 15 µm were demonstrated with a wafer bow of 1 µm, representing the thickest films grown on 150-mm-diameter substrates with low bow to date.

In this paper GaNP/GaP LED structures are much simpler to grow than conventional process, chip processing uses existing technology, and GaNP/GaP LEDs exhibit only a small wavelength shift with injection current. With increasing temperature, the electroluminescence (EL) intensity decreases. Thus, GaNP/GaP LEDs are in the process of being commercialized.