Ravi K. Nadella

Be+/P+, Be+/Ar+, and Be+/N+ coimplantations into InP:Fe

Single‐ and multiple‐energy Be+/P+, Be+/Ar+, and Be+/N+ coimplantations were performed into semi‐insulating InP:Fe. Significantly higher Be dopant activations were obtained for Be+/P+ and Be+/Ar+ coimplantations compared to Be+ implantation. Sharp hole‐concentration depth profiles were obtained for Be+/P+ and Be+/Ar+ coimplantations in contrast to the deep diffusion fronts for Be+ implantation. A high degree of crystalline lattice damage in coimplanted material is believed to be responsible for the improved electrical characteristics of the material. A poor Be dopant electrical activation was observed for Be+/N+ coimplantation.

MeV energy Fe and Co implants to obtain buried high resistance layers and to compensate donor implant tails in InP

High‐energy Fe and Co implantations were performed into InP:Sn at room temperature and 200 °C in the energy range 0.34–5.0 MeV. Range statistics were calculated for these ions in the above energy range. For the room‐temperature implants, implant redistribution peaks around 0.8Rp and Rp+ΔRp, and both in‐ and out‐diffusion of the implant are observed in the secondary‐ion‐mass‐spectroscopy profiles of the annealed samples. The implant redistribution present in the room‐temperature implants is much different than in elevated‐temperature implants. For buried (high‐energy) implants, much of the implant diffusion is eliminated if the implants are performed at 200 °C. For 200 °C implants, the yield of the Rutherford backscattering spectra on the annealed samples is close to that of a virgin sample. The MeV energy Fe and Co implantations at 200 °C are useful to obtain thermally stable, buried, and high‐resistance layers of good crystalline quality in n‐type InP and for the compensation of the tail of the buried n‐...

Rutherford backscattering studies on high-energy Si-implanted InP

High-energy Si-implantations into InP:Fe were examined using Rutherford backscattering (RBS) via channeling measurements. Variable-fluence implantations at 3 MeV and variable-energy implantations for a fluence of 3 x 1014 cm−2 were done. A damagestudy on the 3 MeV Si-implanted samples by RBS indicated formation of a continuous, buried amorphous layer for a fluence of ≈5 x 1014 cm−2. The quality of the crystal in the region of the amorphous layer was poor after annealing at any temperature (≤900° C), indicating that the crystallization during annealing resulted in either a highly defective material or a polycrystal. For samples with damage below the continuous amorphous level, damage recovery is essentially independent of damage concentration. In the variable-energy-implanted samples, the region of damage moved deeper below the sample surface with increasing energy.

High-energy Si implantation into InP:Fe

High‐energy Si implantations were performed into InP:Fe at energies ranging from 0.5 to 10 MeV for a dose of 3×1014 cm−2, and at 3 MeV for the dose ranging from 1×1014 to 2×1015 cm−2. The first four statistical moments of the Si‐depth distribution, namely range, longitudinal straggle, skewness, and kurtosis, were calculated from the secondary‐ion mass spectrometry (SIMS) data of the as‐implanted samples. These values were compared with the corresponding trim‐89 calculated values. SIMS depth profiles were closely fitted by Pearson IV distributions. Multiple implantations in the energy range from 50 keV to 10 MeV were performed to obtain thick n‐type layers. Variable temperature/time halogen lamp rapid thermal annealing (RTA) cycles and 735 °C/10‐min furnace annealing were used to activate the Si implants. No redistribution of Si was observed for the annealing cycles used in this study. Activations close to 100% were obtained for 3×1014‐cm−2 Si implants in the energy range from 2 to 10 MeV for 875 °C/10‐s R...

Elevated‐temperature 3‐MeV Si and 150‐keV Ge implants in InP:Fe

Variable‐fluence 3‐MeV Si+ and 150‐keV Ge+ implants were performed into InP:Fe at 200 °C. Lattice damage in the material is greatly reduced over comparable room‐temperature (RT) implantations and is rather insensitive to fluence for Si+ implantation in the range of 8 × 1014–5 × 1015 cm−2, and no amorphization occurs. For 8 × 1014‐cm−2 Si+ implantation at 200 °C, the dopant activation is 82% and carrier mobility is 1200 cm2/V s after 875 °C/10‐s annealing, whereas for the RT implantation the corresponding values are 48% and 765 cm2/V s, respectively. The reasons for the improved mobility in the elevated‐temperature implants were investigated using Rutherford‐backscattering spectrometry. At a dose of 8 × 1014 cm−2, the aligned yield after annealing is close to that of a virgin sample, indicating a low concentration of residual damage in the 200 °C implant, whereas the lattice remained highly defective in the RT implanted sample. Elevated‐temperature implantation of Si+ and Pi+ ions was also investigated. Co...

MeV B compensation implants into n -type GaAs and InP

High energy B implantations were performed into n‐type GaAs and InP at room temperature in the range of energies from 1 to 5 MeV and fluences from 1011 to 1016 cm−2. The material did not become amorphous for any of the fluences used. Buried layers with resistivities as high as 108 Ω cm and 106 Ω cm were obtained in GaAs and InP, respectively, after heat treatments. The breakdown voltages corresponding to the highest resistivities are 80 and 35 V, respectively, in GaAs and InP. In GaAs, the Rutherford backscattering analysis on the annealed samples showed an aligned yield close to that of a virgin sample, whereas, the yield in InP is more than that of the as‐implanted sample.

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.

Thermally stable, buried high‐resistance layers in p‐type InP obtained by MeV energy Ti implantation

High‐energy Ti+ ions ranging from 1 to 5 MeV were implanted into p‐type InP:Zn (for two different zinc concentrations) at both room temperature and 200 °C. The range statistics for Ti implanted at various energies were calculated by analyzing the as‐implanted profiles determined by secondary‐ion mass spectrometry. Ti did not redistribute during post‐implantation annealing except for a slight indiffusion, irrespective of the implant or annealing temperatures used. This behavior is different from the behavior of other implanted transition metals (Fe and Co) in InP, which redistributed highly when the implants were performed at room temperature. In the MeV Ti‐implanted InP:Zn the background Zn showed a small degree of redistribution. Rutherford backscattering measurements showed a near virgin lattice perfection for 200 °C implants after annealing. Buried layers with intrinsic resistivity were obtained by MeV Ti implantation in InP:Zn (p=5×1016 cm−3).

0.4–3.0‐MeV‐range Be‐ion implantations into InP:Fe

High‐energy (MeV) Be implants in the energy range 0.4–3.0 MeV and dose range 2×1013–6×1014 cm−2 were performed in InP:Fe. Phosphorus coimplantation was used at all Be implant energies and doses to minimize Be redistribution during annealing. For comparison, the Be implant alone was also performed at 1 MeV for a dose of 2×1014 cm−2. The first four moments of the Be implant depth distributions were calculated from the secondary‐ion‐mass spectrometry (SIMS) data on the as‐implanted samples. Variable temperature/time rapid thermal annealing (RTA) cycles were used to activate the Be implant. A maximum of 94% activation was obtained for 875 °C/15‐s RTA on the 2‐MeV/2×1014‐cm−2 Be implant. In contrast to Be‐implanted samples, no in‐diffusion of Be was observed in Be/P‐coimplanted samples. For the annealed samples, two additional Be peaks located at 0.8Rp and 0.9Rp (range) were observed in the SIMS depth profiles.

DC characteristics of high-breakdown-voltage p-i-n diodes made by 20-MeV Si implantation in InP:Fe

A vertical p-i-n diode is made for the first time in InP:Fe using megaelectronvolt energy ion implantation, A 20-MeV Si implantation and kiloelectronvolt energy Be/P coimplantation are used to obtain a buried n/sup +/ layer and a shallow p/sup +/ layer, respectively. The junction area of the device is 2.3*10/sup -5/ cm/sup 2/ and the intrinsic region thickness is approximately=3 mu m. The device has a high breakdown voltage of 110 V, reverse leakage current of 0.1 mA/cm/sup 2/ at -80 V, off-state capacitance of 2.2 nF/cm/sup 2/ at -20 V, and a DC incremental forward resistance of 4 Omega at 40 mA.<<ETX>>