He-plasma assisted epitaxy for highly resistive, optically fast InP-based materials

Abstract

InP and related quaternaries (InGaAsP) have been grown by conventional gas source molecular beam epitaxy while simultaneously exposing the growth surface to a He plasma stream generated by electron cyclotron resonance. For growth temperatures from 400 to 450 °C, the InP produced by this process displays greatly increased resistivity, as high as 105 Ω cm, compared to growth without plasma where resistivities are typically less than 1 Ω cm. An InGaAsP quaternary, with band-gap wavelength of 1.55 μm, grown with the plasma displays a sharp band edge and fast photoresponse (15 ps).

InGaAsP grown by He-plasma-assisted molecular beam epitaxy for 1.55 μm high speed photodetectors

“…1 with a simple exponential, we extracted a free carrier lifetime of ϳ7 a͒ Electronic mail: jin@ccf.nrl.navy.mil ps for both samples. Similar measurements performed at a wavelength of ϳ820 nm with pulses generated by a Ti:sapphire laser produce results comparable to those at 1.55 m. These results are approximately a factor of two shorter than the previously reported lifetime of the undoped InGaAsP at 1.55 m. 1 We used a much lower photogenerated carrier density (ϳ1ϫ10 17 cm Ϫ3 ) for our measurements with free carrier trapping time being dominant, while the results of Mitchell et al 1 were dominated by the trapped carrier recombination. The carrier lifetimes were measured in several different spatial positions on both samples, with the variation in the extracted values being less than 30%.…”

“…1,2 The InGaAsP material is particularly interesting because of its narrow band gap and a high absorption of 1.55 m light, an important quality considering the importance of this wavelength in telecommunications. Life time measurements on carriers photogenerated near the material band gap have shown ϳ15 ps carrier lifetime for undoped InGaAsP samples and as short as ϳ800 fs for beryllium ͑Be͒ doped InGaAsP samples, depending on growth conditions.…”

Quantum well intermixing enhanced by InP grown by He-plasma assisted GaS source MBE

“…These have a much lower diffusivity than P-vacancies [18], hence it appears that, under the anneal conditions used in this work, the upper QW blocks the diffusion of the defects, preventing them from reaching the lower QW. Also, we know that the defects present in the as-grown He * -InP greatly decrease the carrier lifetime [19] and as these diffuse to the QW, they quench the PL emission as observed in figure 5(b).…”

“…The low temperature epitaxial process has recently been extended to include QWI in InP-based materials using a low-temperature grown InP layer [13]. Also, a novel QWI process applied to InP-based laser structures was demonstrated using an epitaxial InP cap layer that was grown with a simultaneous exposure to a He-plasma (He * -InP) produced by an electron cyclotron resonance (ECR) source [14,15]. This unusual InP material incorporates excess point defects into the layer during the growth and these diffuse into the underlying QW structure and enhance the intermixing process during a subsequent anneal treatment.…”