Katsumi Sugiura

Origin of nonradiative recombination centers in AlGaInP grown by metalorganic vapor phase epitaxy

We report the first concrete evidence that oxygen causes nonradiative deep levels in (Alx Ga1–x)0.5In0.5P grown by metalorganic vapor phase epitaxy. We doped AlGaInP with O2 and investigated the oxygen and deep level concentrations by secondary ion mass spectroscopy and isothermal capacitance transient spectroscopy. We confirmed that oxygen causes the D3 (thermal activation energy: ET ≅ 1.0 e V for x = 0.7, nonradiative recombination center) and D2 (ET ≅ 0.46 e V) levels, which we previously found in undoped AlGaInP. We demonstrate that the oxygen and nonradiative deep level concentrations are significantly reduced at higher growth temperatures, higher PH3 partial pressures, and substrate offset from (100) toward [011].

Study on radiative efficiency in AlGaInP/GaInP double-heterostructures : influence of deep level in cladding layers

Abstract We have studied the recombination process of carriers in AlGaInP/GaInP double heterostructures grown by metalorganic vapor phase epitaxy using time-resolved photoluminescence. We found that interfacial recombination is a major process in our samples. We have also studied the influence of the deep-level concentration in AlGaInP-cladding layers on interfacial recombination and found that reducing the deep level concentration from 10 15 to 10 13 cm -3 reduces the interfacial recombination velocity from 140 to 60 cm/s and improves the radiative efficiency. Our results suggest that carriers in the active layer recombine nonradiatively at the interfaces due to the deep level in cladding layers.

Analysis of recombination centers in (AlxGa1−x)0.5In0.5P quaternary alloys

We studied nonradiative recombination centers in undoped (AlxGa1−x)0.5In0.5Pgrown by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. We found three deep energy levels, including a mid‐gap level. We drew an equation to get a capture cross section for minority carriers, and obtained it using isothermal capacitance transient spectroscopy measurement. The mid‐gap level had an electron capture cross section of 2 × 10−10 cm2 and a hole capture cross section of 1 × 10−15 cm2. The time constant of nonradiative recombination through the mid‐gap level was found to be comparable to that of radiative recombination. We concluded that the mid‐gap level is an effective nonradiative recombination center that reduces photoluminescence intensity.

Origin of Nonradiative Recombination Centers in AlGaInP Grown by MOVPE

Nonradiative recombination centers associated with midgap deep levels significantly degrade the radiative efficiency of AlGaInP heterostructures used in visible laser diodes (LDs) and light-emitting diodes (LEDs) in the 600-nm wavelength regionl, 2. We report the first direct evidence that such nonradiative recombination centers in AlGaInP are introduced by oxygen. We quantitatively demonstrate advantages of higher temperature growth and substrate misorientation for reducing the oxygen and, consequently, nonradiative recombination centers. We propose a model for oxygen incorporation mechanisms and defect configurations. We investigated how oxygen is incorporated and affects deep level formation, using secondary ion mass spectroscopy (SIMS) and isothermal capacitance transient spectroscopy (ICTS) for (Als.zGao.g)o.5lns.5P intentionally doped with t6Oz.Epitaxial layers were grown by metalorganic vapor phase epitaxy (MOVPE). The 16C,z concentration in the vapor phase was varied from 0.004 to 0.04 ppm. We obtained a very low SIMS 160 background (1 to 3 x 1g16sm-3) by careful measurement precautions. We studied photoluminescence (PL) intensity for AlGalnP(O2-doped)/GalnP(undoped, 0.02 pm) doublehetero (DH) strucrures. We found that:

Non-Radiative Recombination Center in AlGaInP Quarternary Alloys

lfe investigated deep energy leve1s in undoped-AlGalnP gronn by metal organie vapor phase epitaxy using eapacitanee transient speetroscopy. He found three deep energy levels ineluding a mid-gap level. lle neasured capture cross sections for both eleetrons and holes and confirned the midgap level to be a non-radiative reeombination center by estimating a time eonstant of a non-radiative reconbination. l{e redueed the number of the non-radiative reconbination centers by high temperature gronth and obtained AlGaInP nith high radiative efficiency.