Electrical isolation of GaN by MeV ion irradiation

The evolution of sheet resistance of n-type GaN epilayers exposed to irradiation with MeV H, Li, C, and O ions is studied in situ. Results show that the threshold dose necessary for complete isolation linearly depends on the original free electron concentration and reciprocally depends on the number of atomic displacements produced by ion irradiation. Furthermore, such isolation is stable to rapid thermal annealing at temperatures up to 900 °C. In addition to providing a better understanding of the physical mechanisms responsible for electrical isolation, these results can be used for choosing implant conditions necessary for an effective electrical isolation of GaN-based devices.This work was partly supported by Conselho Nacional de Pesquisas (CNPq, Brazil) under Contract No. 200541/ 99-4

Electrical isolation of n-type and p-type InP layers by proton bombardment

The evolution of the sheet resistance(Rs) of n-type and p-type conductive InP layers during proton irradiation and the stability of the formed isolation during postirradiation annealing were investigated. It was found that the threshold dose (Dth) to convert the conductive layer to a highly resistive one is different for n- and p-type samples with similar initial free carrier concentrations. From our results, one infers that the antisite defects and/or related defect complexes formed by the replacement collisions are the carrier trapping centers, where InP is responsible for electron trapping and PIn for the hole trapping. A time dependence of the Rs was observed after each irradiation step to doses of ≅Dth and higher. This time variation is related to metastable processes involving free carriers. The thermal stability of the isolation of n-type samples is limited to temperatures lower than 200 °C, irrespectively of the irradiated dose. For p-type samples the thermal stability of electrical isolation is extended to 450–500 °C.This work was partly supported by Conselho Nacional de Pesquisas (CNPq, Brazil) under Contract No. 200541/ 99-4

Ultrafast trapping times in ion implanted InP

As⁺ and P⁺implantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1×10¹⁶ cm⁻² and p-type InP was implanted with doses between 1×10¹² and 1×10¹⁶ cm⁻². Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implantedp-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity

Characterization of deep level traps responsible for isolation of proton implanted GaAs

Deep level transient spectroscopy was employed to determine the electrical properties of defects induced in metalorganic chemical-vapor deposition grown n-type and p-type GaAs during proton bombardment. Thermal stability of these defects was investigated and correlation with defects responsible for isolation of GaAs by ion bombardment was discussed. The annealing temperature region (220–250 °C) is similar to proton isolated GaAs below the threshold dose for complete isolation. At least four of the five traps observed in n-type GaAs are not simple interstitial-vacancy pairs. For p-type GaAs we have observed an unknown level with apparent energy of ~0.64 eV

Effect of irradiation temperature and ion flux on electrical isolation of GaN

We study the evolution of sheet resistance of n-type GaN epilayers irradiated with MeV ¹H and ¹²C ions. Results show that both implantation temperature (varied from 77 up to 423 K) and ion beam flux affect the process of electrical isolation in the case of irradiation with ¹²C ions. This behavior is consistent with significant dynamic annealing occurring in GaN during MeV light-ion bombardment, which suggests a scenario where the centers responsible for electrical isolation are defect clusters or anti-site-related defects. Dynamic annealing causes simple ion-beam-generated Frenkel pairs to annihilate (or cluster) during irradiation at liquid nitrogen temperature and above. These beam-flux and irradiation-temperatureeffects are not observed during bombardment with lighter ¹H ions, which produce very dilute collision cascades. A qualitative model is proposed to explain temperature and flux effects in GaN in the MeV light-ion bombardment regime used for electrical isolation

Electrical isolation of n-type and p-type InP layers by proton bombardment

The evolution of the sheet resistance (R s ) of n-type and p-type conductive InP layers during proton irradiation and the stability of the formed isolation during postirradiation annealing were investigated. It was found that the threshold dose (D th ) to convert the conductive layer to a highly resistive one is different for n-and p-type samples with similar initial free carrier concentrations. From our results, one infers that the antisite defects and/or related defect complexes formed by the replacement collisions are the carrier trapping centers, where In P is responsible for electron trapping and P In for the hole trapping. A time dependence of the R s was observed after each irradiation step to doses of ХD th and higher. This time variation is related to metastable processes involving free carriers. The thermal stability of the isolation of n-type samples is limited to temperatures lower than 200°C, irrespectively of the irradiated dose. For p-type samples the thermal stability of electrical isolation is extended to 450-500°C

Electrical Isolation Of A Silicon δ-doped Layer In Gaas By Ion Irradiation

The electrical isolation of a n-type δ-doped layer embedded into undoped GaAs was studied using proton or helium ion bombardment. The threshold dose for isolation Dth of the δ-doped layer was found to be ≈2 times higher than that predicted for thick doped layers of similar carrier concentration. The thermal stability of the isolation, i.e., the persistence of sheet resistance Rs at values > 109Ω/□ after subsequent thermal annealing, is limited to temperatures below 400°C. This temperature limit for the thermal stability Tsm is markedly lower than those observed in wider doped layers in which Tsm is ≅650°C. A previously isolated δ-doped layer presents p-type conductivity after annealing at temperatures >600°C . © 1999 American Institute of Physics.751319171919Shubert, E.F., (1990) J. Vac. Sci. Technol. A, 8, p. 2980Daniltsev, V.M., Irin, I.V., Murel, A.V., Khrykin, O.I., Shashkin, V.I., (1994) Inorg. Mater. (Transl. of Neorg. Mater.), 30, p. 948Zrenner, A., Koch, F., Ploog, K., (1987) Inst. Phys. Conf. Ser., 91, p. 171Van Der Pauw, L.J., (1958) Philips Res. Rep., 13, p. 1De Souza, J.P., Danilov, I., Boudinov, H., (1997) J. Appl. Phys., 81, p. 650Ziegler, J.F., Biersack, J.P., Littmark, U., (1985) The Stopping and Range of Ions in Solids, 1. , Pergamon, OxfordDe Souza, J.P., Danilov, I., Boudinov, H., (1998) J. Appl. Phys., 84, p. 4757De Souza, J.P., Danilov, I., Boudinov, H., (1996) Appl. Phys. Lett., 68, p. 535De Souza, J.P., Danilov, I., Boudinov, H., (1998) Radiat. Eff. Defects Solids, 147, p. 109Grandidier, B., Stiévenard, D., Nys, J.P., Wallart, X., (1998) Appl. Phys. Lett., 72, p. 245