Chiharu Nozaki

Growth temperature dependent atomic arrangements and their role on band-gap of InGaAlP alloys grown by MOCVD

Detailed observation of atomic arrangement in In0.5(Ga1−xAlx)0.5P(0⩽x⩽1) grown by MOCVD with a wide range of growth temperatures Tg (570–770° C) was carried out using electron diffraction and high resolution transmission electron microscopy. A correlation between the atomic arrangement and band-gap energy was studied by photoluminescence and photoacoustic spectroscopy. For Tg≲760° C, the epitaxial layers have ordered structures. For Tg≳770° C, the ordering disappear. Shifts in the band-gap depend on the density of the ordered layers for x≲0.5. For x≳0.5, the band-gap is not affected by the ordering.

Zn doping characteristics for InGaAlP grown by low‐pressure metalorganic chemical vapor deposition

Zn doping characteristics have been studied for In0.5(Ga1−xAlx)0.5P grown by low‐pressure metalorganic chemical vapor deposition, using dimethylzinc (DMZ) as a Zn dopant source. Hole concentration decreased with increasing Al composition x. For low DMZ introduction, the Zn incorporation efficiency decreased with increasing x. For high DMZ introduction, hole concentration saturation occurred as a result of the fall in Zn electrical activity and the Zn electrical activity also decreased with increasing x.

InGaAs/InAlAs HEMT with a strained InGaP Schottky contact layer

The authors have fabricated an InGaAs/InAlAs HEMT structure with a strained InGaP Schottky contact layer to achieve selective wet gate recess etching and to improve reliability for thermal stress. Strained In/sub 0.75/Ga/sub 0.25/P grown on InAlAs has been revealed to have sufficient Schottky barrier height for use as a gate contact. Threshold voltage standard deviation has been reduced to one fifth that of a conventional InGaAs/InAlAs HEMT, as a result of successful selective recess etching. After thermal treatment at 300 degrees C for 5 min, the drain current and transconductance did not change, while those of the conventional HEMT decreased by more than 10%.<<ETX>>

A study of p-type doping for AlGaInP grown by low-pressure MOCVD

Abstract Doping characteristics for Mg (and Zn) in (Al x Ga 1− x ) 0.5 In 0.5 P have been studied with a view towards applying Mg (or Zn) doped AlInP to DH lasers. The solubility limits for the dopants decreased with increasing Al composition. The maximum hole concentration of Zn doped AlInP was at most 2×10 17 cm −3 , which is too low for practical use in DH lasers. The solubility limits for Mg were several times higher than those for Zn. The maximum hole concentration of Mg doped AlInP was 1×10 18 cm −3 . The Mg incorporation was considered to be limited by Mg revaporization from the growth surface. The Mg incorpolation at a constant doping-source introduction in AlGaInP increased with increasing Al composition. The proportion of electrically active Mg to total incorpolated Mg (electrical activity) does not change markedly with Al composition. The Mg electrical activity was quite low even at low doping levels.

Diffuse scattering and superstructure reflections from In1−y(AlxGa1−x)yP

The structure of In1−y (Alx Ga1−x )y P semiconductor alloy systems was studied by electron diffraction. Varied distribution of diffuse scattering and superstructure reflections was observed. The pertinent ordered structure is dependent on growth parameters, but not on the alloy systems. The diffuse scattering could be attributed to mean square atomic displacements due to the coexistence of different column III atoms in the same sublattice.

Reactive Ion Beam Etching and Overgrowth Process in the Fabrication of InGaN Inner Stripe Laser Diodes

Dry etching and overgrowth process techniques have been developed for the fabrication of InGaN inner stripe laser diodes. The dry etch damage at the etched surface and the overgrown interface was estimated using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS). As a result, the etch damage at the overgrown interface was shown to be repaired during the overgrowth. Groove stripes formed on the GaN layer by reactive ion beam etching (RIBE) were overgrown by GaN using metalorganic chemical vapor deposition (MOCVD). The morphology of the overgrown surface was observed by scanning electron microscopy (SEM). The grooves of widths less than 10 µm were buried completely at 1100°C and smooth, flat surfaces were obtained. We have fabricated the InGaN inner stripe (IS) lasers and reported on the first pulsed lasing operation of InGaN inner stripe lasers, fabricated by dry etching and overgrowth techniques.

Surface related degradation of InP-based HEMTs during thermal stress

Abstract Degradation of unpassivated InP HEMTs related to the surface of InAlAs was studied. In ungated HEMTs, the drain current decreased after annealing at temperatures as low as 250°C. RBS measurements revealed that lattice disorder was induced on the surface on InAlAs during thermal treatment, which was considered to be due to either the introduction of vacancies or In segregation. Surface-related degradation was effectively suppressed by passivating devices with SiN layers.

Novel HEMT structures using a strained InGaP Schottky layer

The authors propose a new structure for InGaAs/InAlAs high electron mobility transistors (HEMTs) using a strained InGaP Schottky contact layer to achieve selective wet gate recess etching and to improve reliability for thermal stress. Strained In/sub 0.75/Ga/sub 0.25/P grown on InAlAs has been revealed to have sufficient Schottky barrier height for use as a gate contact. InGaAs/InAlAs HEMTs using an In/sub 0.75/Ga/sub 0.25/P layer have been grown by metal-organic chemical vapor deposition and 1/spl mu/m-gate devices have been fabricated. High selectivity in gate recess etching and higher reliability during thermal treatment have been demonstrated.<<ETX>>

A deep level in Zn‐doped InGaAlP

A deep level in Zn‐doped In0.5(Ga1−xAlx)0.5P (x=0–1.0) has been studied by using pulsed‐bias transient capacitance measurements and photocapacitance measurements. One major deep level was found for the entire alloy composition range (x=0–1.0). The deep‐level concentration was proportional to Zn concentration for x=0.4. The ratio of the deep‐level concentration to Zn concentration increased slightly with x. The energy depth from the valence‐band maximum increased with x, from 0.04 eV at x=0 to 0.42 eV at x=1.0. The energy position, referred to as the vacuum state, is essentially invariable for 0<x<1. This level was considered to have a small lattice relaxation. It seemed that this level originates from Zn‐related defects.

Scatterings of Shallow Threshold Voltage on Si-Implanted WN Self-Alignment Gate GaAs Metal-Semiconductor Field-Effect Transistors on Different Composition 2-Inch Substrates by Growing in Three Kinds of Furnaces

Two-inch undoped GaAs crystal boules were grown from different composition melts in a pyrolytic boron nitride crucible in three kinds of furnaces in order to survey composition effect through a consecutive thermal cooling cycle after crystallization on Vth scattering of Si-implanted metal-semiconductor field-effect transistors (MESFETs). On the substrates (dislocation density: 2×103-105 cm-2 order) obtained from the crystal boules, a tungsten nitride self-alignment gate MESFET array of shallow Vth (3×1012 cm-2, 50 keV) was fabricated, and Vth scatterings were observed on them. The Vth scattering for the most As-rich melt-grown crystal boule in the furnace with the smallest ratio of bottom heating was the smallest as compared with those for the slightly Ga-rich or As-rich melt-grown crystal boules in the furnaces with the greatest ratio of bottom heating. There was an anticorrelation between the Vth scattering amplitude and carbon content in the substrate crystals.