Harry B. Dietrich

GaN FETs for microwave and high-temperature applications

Abstract The d.c., microwave, and high-temperature characteristics of Si-doped MESFETs with and without n+ ohmic contact layers, Si 3 N 4 GaN MISFETs, and AlN GaN HFETs are presented. The highest transconductance and microwave performance were observed for 1 μm gate-length HFETs. These HFETs have a transconductance of 45 mS/mm, an ƒ τ of 8 GHz, and an ƒ max of 22 GHz. The Si-doped MESFETs have good pinch-off characteristics at 400°C and are operational at 500°C. Published by Elsevier Science Ltd.

Damaged-induced isolation in n-type InP by light-ion implantation

Abstract A detailed study of the insulating properties of ion-implantation induced damage in InP has been carried out for H, He, B and Be implantation. For each ion, there was found to be an optimal implantation fluence for the formation of resistive layers. At this fluence, a maximum resistivity of 10 3 to 10 4 Ω·cm was observed. Lower resistivities were observed for higher and lower implantation fluences. The primary anneal stage for the maximum resistivity layers was between 250 and 300°C. Anomalous results were observed for H implantation in that the resistivity observed depends on the test structure geometry. Measurements carried out by contacting the front and back of the damage layer gave resistivity values two orders of magnitude greater than those measured by contacting adjacent points on an epitaxial structure. For all other ions, the results obtained for the two geometries were in good agreement. It has been shown that a conductive layer produced by the proton bombardment of the underlying Fe-doped substrate gives rise to a low resistance shunt in the epitaxial study.

Light‐ion‐bombarded p‐type In0.53Ga0.47As

Multiple‐energy H‐, He‐, and B‐ion bombardments were performed to obtain uniform high resistivity over the entire thickness of p‐type In0.53Ga0.47As. High resistivity, 580 Ω cm, which is close to the intrinsic resistivity limit of ≊103 Ω cm in InGaAs, is observed. The thermal stability of the high‐resistance layers depended upon the mass of the implanted ion. The B‐ion‐implanted layers maintained high resistivity up to ≊200 °C. Photoluminesence measurements were used to obtain the energy of compensating levels produced by light‐ion bombardment.

Transition metal implants in In0.53Ga0.47As

Single‐ and multiple‐energy Fe, Cr, and V ions were implanted into InGaAs. Annealing of the implanted InGaAs samples caused a redistribution of the implanted atoms, as determined by secondary ion mass spectrometry. Coimplantation of Fe with P did not prevent this redistribution. A transport equation calculation of Fe‐implantation‐induced stoichiometric disturbances in InGaAs was done. The lattice quality of implanted InGaAs was investigated by photoreflectance measurements. Fe‐implanted InGaAs has a resistivity close to the intrinsic limit, whereas Cr‐ and V‐implanted InGaAs have a lower resistivity than the unimplanted material.

MeV Si implantation in GaAs

Abstract The formation of n-type layers in semi-insulating, LEC GaAs by MeV Si implantation has been investigated using an electrolytic CV technique. The study has been done as a function of dose and anneal temperature. The carrier concentration profile associated with 2.5 × 1013/cm2, MeV Si implant was not greatly affected by varying the anneal temperature from 750°C to 840°C. The percentage of activation was 65% for 2.5 × 1013 Si/cm2 and 40% for 5 × 1013 Si/cm3. A buried n-layer with a peak carrier concentration at 2.9 μm was formed with 6 MeV Si implantation. The peak carrier concentration obtained with 4.2 × 1013 Si/cm2 implants was 30% higher with an 850°C anneal than with a 750°C. The percentage of activation was sensitive to dose, decreasing for a dose greater than 4.2 × 1013 Si/cm2. A 3 μm, 2 × 1016/cm3 n-type layer has been produced using multiple MeV Si implantation.

10–20 MeV energy range Si implantations into InP:Fe

Si implantations in the energy range 10–20 MeV were performed into InP:Fe with a dose of 4×1014 cm−2. The secondary‐ion mass spectrometry profiles for the as‐implanted samples were used to calculate the first four statistical moments of the Si implant distribution. Either 875 °C/10 s rapid thermal annealing or 735 °C/10 min furnace annealing was used to activate the Si implants. No redistribution of Si was observed after annealing. Electrochemical capacitance‐voltage profiling was performed on the annealed samples to obtain the carrier concentration depth profiles. Activations of 90%–100% and peak carrier concentrations of 3–4×1018 cm−3 were measured for 10–20 MeV Si implants after 875 °C/10 s rapid thermal annealing.

Atomic profiles and electrical characteristics of very high energy (8–20 MeV) Si implants in GaAs

High‐energy Si implantation into GaAs is of interest for the fabrication of fully implanted, monolithic microwave integrated circuits. Atomic concentration profiles of 8, 12, 16, and 20 MeV Si have been measured using secondary ion mass spectroscopy (SIMS). The range and shape parameters have been determined for each energy. The theoretical atomic concentration profile for 12 MeV Si calculated using TRIM‐88 corresponded to the SIMS experimental profile. No redistribution of the Si was observed for either furnace anneal, 825 °C, 15 min, or rapid thermal anneal, 1000 °C, 10 s. The activation of the Si improved when coimplanted with S. The coimplanted carrier concentration profiles did not show dopant diffusion. Peak carrier concentration of 2×1018/cm3 was obtained with a Si and S dose of 1.5×1014/cm2 each.

MeV Be implantation in GaAs

High‐energy Be implantation was performed at 1, 2, and 3 MeV for a dose of 1×1013 cm−2 and at 2 MeV in the dose range of 4×1012–1×1014 cm−2. Range statistics from as‐implanted secondary ion mass spectrometry profiles were calculated. The implanted wafers were activated by either conventional furnace or rapid thermal annealing. For the same implant dose, 1×1013 cm−2, the dopant electrical activation decreased with increasing ion energy. For the 2‐MeV implants, the dopant electrical activation increased with the implant dose, in the range used in this study. An activation as high as 98% was measured for the 2‐MeV/1×1014‐cm−2 Be implant.

Co, Fe and Ti implants in InGaAs and Co implants in InP at 200° C

Elevated temperature (200° C) single- and multiple-energy Co implants inn-type InP, Co and Fe implants in n-type In0.53Ga0.47As, and Ti implants inp-type In0.53Ga0.47As were performed. For elevated temperature, single-energy Co and Fe implants, no satellite peaks at various locations like 0.8RP, RP+ ΔRP, and 2RPRP is the projected range and ΔRP the straggle of the implant) are observed, in contrast to the case of room temperature implants. However, the outdiffusion of the implant is as severe as that in room temperature implantation for high temperature anneals. Indiffusion of the implant also occurs, but it is not as severe as the outdiffusion. High temperature annealing of Ti-implanted material results in a slight indiffusion of Ti, with minimal redistribution or outdiffusion. For all elevated temperature implants, the lattice quality of the annealed material is close to that of the virgin unimplanted material. For all ion species used in this study, resistivities close to the intrinsic limit are obtained in the implanted and annealed materials.

Range statistics and Rutherford backscattering studies on Fe‐implanted In0.53Ga0.47As

Single‐energy Fe implantation at energies in the range 50 keV–2 MeV to achieve a peak Fe concentration of 1–2×1018 cm−3 is performed into undoped (n‐type) InGaAs layers grown on InP:Fe. The first four statistical moments of the Fe profiles measured by secondary‐ion mass spectrometry are determined. The Pearson IV distribution calculated from these moments matches the implant‐profile closely. Samples implanted with Fe to doses in the range 5x1012 –2×1015 cm−2 at 380 keV are analyzed by Rutherford backscattering measurements to study ion‐induced damage. For 380‐keV implants, amorphization begins at a dose of ≊3×1013cm−2.