The reverse breakdown voltage of p-GaN Schottky diodes was used to measure the electrical effects of high density Ar or H2 plasma exposure. The near surface of the p-GaN became more compensated through introduction of shallow donor states whose concentration depended on ion flux, ion energy, and ion mass. At high fluxes or energies, the donor concentration exceeded 1019 cm−3 and produced p-to-n surface conversion. The damage depth was established as ∼400 Å based on electrical and wet etch rate measurements. Rapid thermal annealing at 900 °C under a N2 ambient restored the initial electrical properties of the p-GaN.

We report on the growth and characterization of ultraviolet GaN quantum well light emitting diodes. The room-temperature electroluminescence emission was peaked at 353.6 nm with a narrow linewidth of 5.8 nm. In the simple planar devices, without any efforts to improve light extraction efficiency, an output power of 13 μW at 20 mA was measured, limited in the present design by absorption in the GaN cap layer and buffer layer. Pulsed electroluminescence data demonstrate that the output power does not saturate up to current densities approaching 9 kA/cm2.

A GaN/AIGaN heterojunction bipolar transistor structure with Mg doping in the base and Si doping in the emitter and collector regions was grown by Metal Organic Chemical Vapor Deposition on c-axis A1203. Secondary Ion Mass Spectrometry measurements showed no increase in the 0 concentration ( 2 -3~1 0 '~ ~m -~) in the AlGaN emitter and fairly low levels of C (-4-5~10'~ cm-3) throughout the structure. Due to the non-ohmic behavior of the base contact at room temperature, the current gain of large area (-90 pm diameter) devices was <3. Increasing the device operating temperature led to higher ionization fractions of the Mg acceptors in the base, and current gains of -10 were obtained at 300 OC. 1There is a strong interest in GaN-based electronics for applications involving high temperature or high power operation, based on the excellent transport properties of the III-nitride materials system.(*-7' Impressive advances in the performance of AlGaN/GaN high electron mobility transistors continue to be reported, due to in part to the formation of piezoelectrically-induced carriers in a 2-dimensional electron gas at the There is also interest in the development of GaN/AIGaN In this letter we report on the growth by MOCVD of a graded emitter HBT structure, DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document.Spectrometry (SIMS) since these could potentially have a strong influence on device performance, and finally on the dc characteristics of HBTs fabricated on this material.The layer structure is shown schematically in Figure 1, and was grown at -1050 "C following deposition of the GaN buffer at -550 "C on the c-plane A1203 substrate. The growth system has been described in detail previously,'2o' but in brief is a rotating (1200 rpm) disk MOCVD reactor. Ammonia (NH3), trimethylgallium (TMGa) and trimethylaluminum (TMAl) were used as precursors, while silane (SiH4) and biscyclopentadienyl-magnesium (CpzMg) were employed for n-and p-type doping, respectively. High purity H2 was used as the carrier gas. After growth the sample was annealed in the reactor at 850 "C for 20 min under 140 Torr of flowing N2 to activate the Mg acceptors.There are two important aspects to dopant and background impurity control in HBT structures. The first is that the p-type dopant should be confined to the base region, and not spill-over into the adjacent n-type emitter, where it could cause displacement of the junction and hence the loss of the advantage of the heterostructure. Figure 2 shows SIMS profiles of the A1 marker, signifying the position of AlGaN emitter layer, and also the Mg doping profile in the adjacent base layer. It is clear that the reactor memory effect for Cp2Mg has produced incorporation of Mg in the emitter, although the real situation is not quite as severe as it seems in the data because of "carry-over" of the matrix A1 signal during the depth profiling. The fact that working HBTs can still be made on this material is due...

ABSTRACTcalculated from the measured g , and the source series resistance, is 81 mS/mm. The fT and fmax for these devices are 6 GHz and 12 GHz, respectively. These JFETs exhibit a significant current reduction after a high drain bias is applied, which is attributed to a partially depleted channel caused by trapped hot-electrons in the semi-insulating GaN buffer layer. A theoretical model describing 1 the current collapse is described, and an estimate for the length of the trapped electron region is given.

The effects of H2 or N2 plasma exposure on the current–voltage characteristics of GaN Schottky diodes were examined as a function of source power and rf chuck power. Under all conditions there was a strong reduction in diode reverse breakdown voltage and an increase in forward and reverse currents. The results are consistent with creation of a thin (⩽600 Å) n-type conducting surface region after ion bombardment of the GaN surface. Much of the degradation in diode quality can be recovered by annealing in N2 at 750 °C.