AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with 2 MeV protons, carbon, oxygen, iron and krypton ions with fluences ranging from 1 × 109 cm−2 to 1 × 1013 cm−2. DC, pulsed I–V characteristics, loadpull and S-parameters of the AlGaN HFET devices were measured before and after irradiation. In parallel, a thick GaN reference layer was also irradiated with the same ions and was characterized by X-ray diffraction, photoluminescence, Hall measurements before and after irradiation. Small changes in the device performance were observed after irradiation with carbon and oxygen at a fluence of 5 × 1010 cm−2. Remarkable changes in device characteristics were seen at a fluence of 1 × 1012 cm−2 for carbon, oxygen, iron and krypton irradiation. Similarly, remarkable changes were also observed in the GaN layer for irradiations with fluence of 1 × 1012 cm−2. The results found on devices and on the GaN layer were compared and correlated.
AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1x107 to 1x1013 cm-2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1x1010 cm-2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5x1010 cm-2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1x1012 cm-2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1x1012 cm-2. The device results and GaN layer properties are strongly correlated.
The effect of proton, carbon, oxygen and krypton irradiation on AlGaN HFET devices has been studied. Irradiation was performed at 68 and 120 MeV with fluences in the range from 1 × 10^7 to 1 × 10^13 cm2 . Before and after irradiation, dc and pulsed I – V characteristics, loadpull and S -parameters of the AlGaN HFET devices were measured. A thick GaN reference layer was characterized by x-ray diffraction, photoluminescence and Hall measurements before and after irradiation. Proton, carbon and oxygen irradiation show no degradation in devices while krypton irradiation shows a small change at a fluence of 1 × 10 10 cm2 in the device characteristics. The device results are correlated with the thick GaN results.
Fabrication and Electrical Performance of Oscillators in GaAs/GaInP-HBT MMIC Technology up to 40 GHz
(2002)
Coplanar W-band push-push VCO MMICs using GaInP/GaAs HBTs are presented. One circuit operates at 77 GHz with phase noise of -92 dBc/Hz at 1 MHz offset. To our knowledge this is the first fully monolithic W-band VCO with phase noise better than -90 dBc/Hz. A second version with two varactor diodes yields an almost threefold relative tuning bandwidth.
Monolithic coplanar 18 and 36 GHz oscillators with GaInP/GaAs-HBTs and on-chip resonators are presented. Measured phase-noise reaches -93 dBc/Hz and -91 dBc/Hz at 100 kHz offset for 18 and 36 GHz, respectively. These values demonstrate that GaAs-HBT oscillators yield a phase-noise performance comparable to SiGe-HBTs, with the potential for higher frequencies.
Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset.
DC and RF characteristics of AlGaN/GaN HEMTs processed by 2-inch stepper lithography are presented. The devices, grown by MOVPE on 2" sapphire wafers consist of: GaN buffer, Al0.25Ga0.75 N spacer, doped Al0.25Ga0.75N supply layer, Al0.25Ga0.75N barrier, GaN cap. Refractory source and gate contacts along with mesa isolation and air bridge technology are applied. Typical values for maximum saturation current, transconductance and pinch-off voltage are: 616 m/A/mm, 203 mS/mm, -3.5 V with very good homogeneity across 2". The cut off frequencies fT and fmax are 24 and 54 GHz respectively. A standard small signal equivalent circuit model exactly describes DC- and microwave properties
We report on the technology and performance of fully monolithic coplanar voltage-controlled oscillators (VCOs) with GaInP/GaAs-HBTs as the active devices. With our optimized HBT process, the parasitic base resistance R/sub B/ and extrinsic base-collector capacitance C/sub EX/ are significantly reduced. In this way, the maximum frequency of oscillation F/sub max/ is increased from 100 to 170 GHz. This allows us to realize fundamental 38 GHz-VCOs with very low phase noise. At an oscillation frequency F/sub res/=34.2/spl plusmn/0.2 GHz, the VCO reaches phase noise levels of -87 dBc/Hz @ 100 kHz and -108 dBc/Hz @ 1 MHz offset frequency, respectively. To our knowledge, these phase noise values are the lowest GaAs data for Ka-band applications reported so far.
High-power GaInP/GaAs HBTs with high breakdown voltage for X-band applications are presented. To demonstrate the capabilities of these devices, a simple monolithic amplifier is realized. For a single 12-finger device with 2/spl times/70 /spl mu/m/sup 2/ emitter finger size, an output power of 3.2 W at 9 GHz with 47% PAE is achieved.