Mitsuo Hoshiyama

Discrimination of Compound Semiconductor Heterointerfaces by Simultaneous Observations of Atomic Force Microscopy and Lateral Force Microscopy

ZnSe/GaAs heterointerfaces were studied with simultaneous probing by atomic force microscopy (AFM) and lateral force microscopy (LFM). Surface flatness of the (110) cleaved facets was examined with AFM and the frictional force was measured across the heterointerfaces with LFM. On (110) cleaved facets where ZnSe and GaAs surfaces are located on the same horizontal plane with atomic precision and are not distinguishable with AFM, different frictional forces between ZnSe and GaAs surfaces are observed with LFM. This demonstrates the possibility that the geometrical flatness and the difference of semiconductors on cleaved facets of semiconductor heterointerfaces are distinguished with the simultaneous probing of AFM and LFM, respectively. Abruptness of the ZnSe/GaAs heterointerfaces was found to be drastically improved by replacing ZnSe with ZnSe/ZnS0.18Se0.82 superlattices lattice-matched to GaAs.

p-type conductivity control of ZnSe with insertion of ZnTe:Li submonolayers in metalorganic molecular-beam epitaxy

p-type ZnSe with periodic insertion of ZnTe:Li submonolayers was grown by metalorganic molecular-beam epitaxy. The net acceptor concentration, NA–ND, up to 2×1017–5×1018 cm−3 was observed. However, under higher Li doping, reduction of the growth rate was observed and the growth direction of the islands on the surface changed from the [011] to [011] direction. This resulted in samples not uniformly doped along the growth direction especially for higher Li doping. This reduction of the growth rate was attributed to the adsorption of Li to the B steps, and this phenomenon was suppressed by a periodic Zn purge to the growing surface. By this method, we could keep the growth rate constant and succeeded in obtaining samples which are doped uniformly along the growth direction for higher Li doping. NA–ND up to 4.5×1017 cm−3 was measured in this way. The photoluminescence peaks were blueshifted and discrete peaks were observed with increasing Li doping. This interesting behavior was explained with a ZnTe quantum...

Metalorganic MBE growth of nitrogen-doped ZnSe : TAN doping and nitrogen plasma doping

Growth of ZnSe and nitrogen doping were carried out by metalorganic molecular beam epitaxy (MOMBE). In this study metalorganic precursors were introduced into the growth chamber directly without precracking. We studied two nitrogen doping techniques. First, doping with the nitrogen precursor triallylamine (TAN) was studied. It was found that TAN decomposes above 300°C by quadrupole mass spectrometry. The doping properties of TAN were critically dependent on the VI/II ratio during growth. However contrary to our expectation, the doped ZnSe films tended to be n-type. The other nitrogen-doping technique involves doping with nitrogen gas activated by an electron cyclotron resonance plasma. In the samples doped with the nitrogen plasma, donor-acceptor pair emission was dominant. The net acceptor concentration up to 2.3 x 10 17 cm -3 was measured in samples grown using this doping technique.

Metalorganic molecular beam epitaxy growth of ZnSe with new Zn and Se precursors without precracking

Abstract We report the first successful precracking-free metalorganic molecular beam epitaxy of ZnSe on GaAs (001) substrates. New precursors are diisopropyl zinc (DiPZn), Zn(i-C 3 H 7 ) 2 for Zn, and ditertiarybutyl selenide (DtBSe), Se(t-C 4 H 9 ) 2 for Se. It is found that these precursors decomposed at low temperatures, such as 100°C for DiPZn and 150°C for DtBSe. This decomposition of the precursors at low temperatures allows us to grow ZnSe on GaAs substrates without precracking. Growth rate is the largest at substrate temperature of 350°C and VI II ratio of 12. Under these conditions, the growth rate increases up to 0.6 μm/h.