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In this work, we report on the selective area growth (SAG) of InGaN multiple quantum well (MQW) structures to completely suppress the phenomenon of the Stokes shift in monolithically integrated photonic chips. The original green MQW region is designed as the integrated photodetector (PD), while the SAG blue MQW region acts as the integrated light-emitting diode (LED). The detection spectra of the PD can completely cover the emission spectra of the LED, greatly improving the on-chip optical connection by the complete suppression of the Stokes shift. Thus, the bottleneck of on-chip optical connection based on spectra-tail overlap in integrated photonic chips has been broken. Under the same operating current, the photocurrent of the SAG integrated PD reaches 11.8 μA, while the conventional chip achieves only 0.6 μA. By SAG method, the photo-to-dark current ratio of integrated PD exhibits about two orders of magnitude increase under 0 V bias. Undoubtedly, the SAG technology provides a strategy to further improve the on-chip optical signal transmission efficiency of the MQW structure integrated photonic chips. [ABSTRACT FROM AUTHOR]

The realization of high quality (0001) GaN on Si(100) is paramount importance for the monolithic integration of Si‐based integrated circuits and GaN‐enabled optoelectronic devices. Nevertheless, thorny issues including large thermal mismatch and distinct crystal symmetries typically bring about uncontrollable polycrystalline GaN formation with considerable surface roughness on standard Si(100). Here a breakthrough of high‐quality single‐crystalline GaN film on polycrystalline SiO2/Si(100) is presented by quasi van der Waals epitaxy and fabricate the monolithically integrated photonic chips. The in‐plane orientation of epilayer is aligned throughout a slip and rotation of high density AlN nuclei due to weak interfacial forces, while the out‐of‐plane orientation of GaN can be guided by multi‐step growth on transfer‐free graphene. For the first time, the monolithic integration of light‐emitting diode (LED) and photodetector (PD) devices are accomplished on CMOS‐compatible SiO2/Si(100). Remarkably, the self‐powered PD affords a rapid response below 250 µs under adjacent LED radiation, demonstrating the responsivity and detectivity of 2.01 × 105 A/W and 4.64 × 1013 Jones, respectively. This work breaks a bottleneck of synthesizing large area single‐crystal GaN on Si(100), which is anticipated to motivate the disruptive developments in Si‐integrated optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this work, we present a stress-free AlN film with improved crystal quality assisted by h-BN and demonstrate the mechanical exfoliation of wafer-scale single-crystal AlN freestanding membrane and reveal the controllable exfoliation mechanism of AlN. Uniform and continuous wafer-scale h-BN is directly grown on c-plane sapphire using a flow modulation epitaxy mode by metal-organic chemical vapor deposition. The nucleation and evolution processes of quasi-van der Waals epitaxy (QvdWE) of AlN on h-BN are revealed. It is found that O2-plasma-treated h-BN can effectively promote the nucleation islands of AlN and contribute to the release of biaxial stress and the reduction of dislocation density in the epilayers. Eventually, the QvdWE growth of a stress-free AlN film (0.08 GPa) is achieved, and wafer-scale mechanical exfoliation of the AlN membrane has been realized. This work provides an effective strategy for the quality improvement of III-nitride films and paves the way for the vertical structure and flexible deep-ultraviolet optoelectronic devices. [ABSTRACT FROM AUTHOR]

For developing p-GaN gate-based enhancement-mode AlGaN/GaN high-electron-mobility transistors, the removal of the p-GaN layer around the gate region is demonstrated by photo-electrochemical etching. The etching behavior of p-GaN/AlGaN/GaN heterostructures along with p-GaN/u-GaN reference samples is investigated in acidic H2SO4/H3PO4 electrolyte solution. The strong oxidant sulfate radical SO 4 − ∗ formed by H2SO4 stimulates the etching process by either extracting excess electrons from the valence band or providing supplementary holes in the valence band. By optimizing the etching parameters, an average etching rate of 0.27 nm/min with a surface roughness of 2.3 nm is achieved for removing p-GaN from the AlGaN/GaN structure. The etching dynamics of the heterostructure are attributed to the valence-band offset ΔEv caused by band discontinuity at the p-GaN/AlGaN interface. Under positive anodic bias, the etching process is also controlled by local charge transport between p-GaN and the two-dimensional electron gas channel due to a reduced barrier height. [ABSTRACT FROM AUTHOR]

In this letter, quasi-vertical Schottky barrier diodes (SBDs) based on AlN/Al0.6Ga0.4N heterostructure are fabricated and temperature-dependent current transport is systematically investigated. Benefited from the AlN/Al0.6Ga0.4N heterostructure with high net doping concentration of ∼1 Ă— 1018 cmâˆ'3 in Al0.6Ga0.4N, the device demonstrates lower ideality factor of 2.95, high on/off current ratio of ∼108, the on-current of above 40 A cmâˆ'2 which is two order magnitude higher than that of the state-of-the-art AlN SBDs. The barrier inhomogeneity is characterized by the model of Gaussian distribution, and the reverse current observed is identified to be traps-related leakage process such as Pooleâ€"Frenkel emission and trap assisted tunneling. This work reveals the heterostructure engineering is an alternative pathway to overcome the difficulty of AlN-based SBDs. [ABSTRACT FROM AUTHOR]

The Al x Ga1 − x N/Al y Ga1 − y N multiple quantum well (MQW) structure for deep ultraviolet emission has been grown on sapphire by metal organic chemical vapor deposition (MOCVD). High resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM), and cathodoluminescence (CL) are used to characterize the structural and optical properties of MQWs, respectively. Clear step flows can be observed in the AFM image indicating a two-dimensional growth model. There are many cracks on the surface of the MQW structure because of the high tensile stress. HRXRD shows multiple satellite peaks to the 2nd order. The HRXRD simulation shows that the MQW period is about 11.5 nm. The emission peak of Al x Ga1 − x N/Al y Ga1 − y N MQWs is about 295 nm in the deep ultraviolet region from the CL spectra. [ABSTRACT FROM AUTHOR]

Al x Ga1- x N ternary alloys are very attractive materials for application to ultraviolet (UV) photodetection. In this work, high Al content Al x Ga1- x N films are grown on sapphire substrate by low pressure metalorganic chemical vapor deposition (MOCVD). The Al content in the Al x Ga1- x N epilayer is estimated to be 54% by high resolution X-ray diffraction (HRXRD) and Vegard’s law. The full width at half maximum (FWHM) of the rocking curve for the Al0.54Ga0.46N (0002) is about 597 arcsec. According to the transmittance measurement result, our sample is suitable for fabricating solar-blind photodetectors. The observed Fabry-Perot fringes in the transmission region indicate that high optical quality is obtained. Solarblind metal-semiconductor-metal (MSM) photodetectors based on the MOCVD-grown Al0.54Ga0.46N film are fabricated and tested. The detector has a low dark current of about 31 pA under a bias voltage of 5 V. An UV/visible contrast of about four orders of magnitude is observed and responsivity increases with increments of the bias voltage. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistor (HEMT) structures were grown on 2 inch sapphire substrates by MOCVD, and 0.8-µm gate length devices were fabricated and measured. It is shown by resistance mapping that the HEMT structures have an average sheet resistance of approximately 380 Θ/sq with a uniformity of more than 96%. The 1-mm gate width devices using the materials yielded a pulsed drain current of 784 mA/mm at V gs=0.5 V and V ds=7 V with an extrinsic transconductance of 200 mS/mm. A 20-GHz unity current gain cutoff frequency ( f T) and a 28-GHz maximum oscillation frequency ( f max) were obtained. The device with a 0.6-mm gate width yielded a total output power of 2.0 W/mm (power density of 3.33 W/mm) with 41% power added efficiency (PAE) at 4 GHz. [ABSTRACT FROM AUTHOR]