Chong-Yi Lee

Growth and characterization of single‐heterostructure AlGaAs/InGaP red light‐emitting diodes by liquid‐phase epitaxy

High quality Te‐doped Al0.7Ga0.3As/Mg ‐doped In0.5Ga0.5P on p‐type GaAs substrate single‐heterostructure light‐emitting diodes have been reproducibly fabricated by liquid‐phase epitaxy using a supercooling technique. The growth conditions and properties of the undoped and Mg‐ and Zn‐doped In0.5Ga0.5P layers are described in detail. The strongest photoluminescence peak intensity occurs at a hole concentration of 1×1018 cm−3 of the Mg‐doped layer. Diodes fabricated from the heterostructure are characterized by electron‐beam‐induced current, current‐voltage measurement, electroluminescence, light output power, and external quantum efficiency. By appropriately controlling the hole concentration of the Mg‐doped In0.5Ga0.5P active layer and the electron concentration of the Te‐doped Al0.7Ga0.3As window layer, the p‐n junction can be precisely located at the metallurgical junction as measured by the electron‐beam‐induced current technique. A forward‐bias turn‐on voltage of 1.5 V with an ideality factor of 1.65 a...

The influence of window layers on the performance of 650 nm AlGaInP/GaInP multi-quantum-well light-emitting diodes

In this article, we investigate the influence of AlGaAs and GaP window layers on the device performance of 650 nm AlGaInP/GaInP multi-quantum-well (MQW) light-emitting diodes (LEDs) grown by metalorganic chemical-vapor deposition. The AlGaInP/GaInP MQW structure with different window layers are characterized by double-crystal X-ray diffraction, secondary ion mass spectrometry and photoluminescence. By using the AlGaAs window layer, the LEDs have a lower cut-in voltage, a smaller dynamic series resistance and a higher breakdown voltage, while the LEDs with a GaP window layer show a stronger electroluminescence intensity, a higher light output power, a higher external quantum efficiency and a slower degradation of light output with increasing bias current. These results indicate that the GaP material is more adequate to be used as a window layer for the AlGaInP optical devices.

Comparison of single‐ and double‐heterostructure AlGaAs/InGaP red light‐emitting diodes prepared by liquid‐phase epitaxy

The performance of the AlGaAs/InGaP single‐heterostructure (SH) and AlGaAs/InGaP/AlGaAs double‐heterostructure (DH) light‐emitting diodes (LEDs) is compared. For these two types of LEDs, they have a very shining surface morphology and flat interface. However, the SH LEDs always exhibit better properties than the DH LEDs in the ideality factor, electroluminescence, light output power, and external quantum efficiency. From the x‐ray diffraction measurements, we find that the main problem for the undesirable performance of DH LEDs is attributed to the difficulty of obtaining the high quality InGaP/AlGaAs heterostructure. Furthermore, by the Auger‐depth‐profile measurements, it is found that the P atoms with a very high diffusivity will diffuse into the as‐grown AlGaAs layer during the growth of InGaP and thus destroy the heterostructure quality.

Temperature dependence of photoluminescence from Mg‐doped In0.5Ga0.5P grown by liquid‐phase epitaxy

The temperature dependence of photoluminescence from the Mg‐doped In0.5Ga0.5P layers on (100) GaAs substrates grown by liquid‐phase epitaxy has been studied. At low temperature, the spectra show only two major emission peaks involving intrinsic recombination and conduction–band‐to‐acceptor transition. The intrinsic recombination dominates in the doping concentration range studied (1.0×1017–7.0×1018 cm−3) above 60 K. Below 50 K, these two peaks merged with each other when the doping concentration is higher than 1×1018 cm−3. The temperature dependence of band gap in In0.5Ga0.5P layers determined from the photoluminescence peak energy varies as 1.976 − [7.5 ×10−4 T2/(T + 500)] eV. For the moderately doped concentration (p < 1.4 × 1018 cm−3), the Mg acceptor ionization energy obtained from 50‐K photoluminescent spectra is in the range from 37 to 40 meV.

MOCVD growth of strained multiple quantum well structure for 1.3 μm InAsP/InP laser diodes

Abstract In this article, we describe the growth and characterization for 1.3 μm InAsP/InP strained multiple quantum well (SMQW) laser diodes (LDs) with separate confinement heterostructure grown at 580°C by metalorganic chemical vapor deposition. The grown strained single quantum well (SSQW) stack and strained multiple quantum well (SMQW) structures are characterized using double-crystal X-ray diffraction and photoluminescence (PL) to confirm the structural and optical qualities for practical device applications. The InAsP/InP SSQW stack grown at 580°C appears to be extremely abrupt, uniform, free of misfit dislocations and narrow PL half width. Although the InAsP/InP SMQWs grown at 580°C maintain its structural integrity throughout the deposition sequence, the slightly broader PL half width for InAsP/InP SMQW structure is attributed to the dislocations resulted from a large net strain. Laser emission can be achieved by using the InAsP/InP SMQWs and the lasing wavelength is in a good agreement with our designed structure. The experimental data of broad-area and ridge waveguide LDs are described in detail.

Mobility and charge density tuning in double δ-doped pseudomorphic high-electron-mobility transistors grown by metal organic chemical vapor deposition

In this article, the authors present mobility and charge density tuning for metal organic chemical vapor deposition (MOCVD)-grown double δ-doped pseudomorphic high-electron-mobility transistors (PHEMTs). Good epitaxial wafers were obtained by MOCVD as indicated by uniform and abrupt interfaces seen in measurements taken using a transmission electron microscope and two pronounced Si-δ-doped peaks in the secondary ion mass spectrometry analysis. The 1-μm-gate-length PHEMT device exhibited good dc performance with a threshold voltage of −1.34V, a maximum drain current of 570mA∕mm, and a maximum transconductance of 279mS∕mm. From the dependences of mobility and charge density between the δ-doping level and spacer layer thickness, most PHEMT design requirements in the ranges between 5750 and 7500cm2∕Vs (for mobility) and 2.4×1012 and 3.6×1012cm−2 (for charge density) can be satisfied.

Mobility and Charge Density Tuning in Double-Doped Enhancement-Mode Pseudomorphic High-Electron-Mobility Transistors Grown by Metalorganic Chemical Vapor Deposition

We present mobility and charge density tuning for metalorganic chemical vapor deposition (MOCVD)-grown double-doped enhancement-mode (E-mode) pseudomorphic high-electron-mobility transistors (PHEMTs) by varying the supplier layer doping level and spacer layer thickness. From the resolvable Pendellosung oscillation in double-crystal X-ray diffraction measurements and a pronounced two-dimensional electron-gas peak in capacitance–voltage (C–V) analyses, good epitaxial wafers are obtained by MOCVD. The 1-µm-gate-length E-mode PHEMT device exhibits a good pinch-off characteristic with a threshold voltage of 0.025 V and a maximum transconductance of 203 mS/mm. The dependences of the pinch-off characteristic in C–V measurement on sheet carrier concentration and spacer layer thickness for E-mode PHEMT application is also described in detail.

Influence of growth temperature of InAsP/InP strained multiple quantum wells grown by metalorganic chemical vapor deposition

In this article, we report the influence of growth temperature on the luminescent and structural properties of InAsyP1−y/InP strained multiple quantum wells (SMQWs) and strained single quantum wells (SSQWs) grown by metalorganic chemical vapor deposition (MOCVD). The strained quantum wells are characterized by high-resolution transmission electron microscope (TEM), photoluminescence (PL), and double-crystal x-ray diffraction (DC-XRD). An AsH3/(AsH3+PH3) gas flow ratio of 0.50% and 1.48% at 580 and 650 °C growth temperatures, respectively, will result in an InAsP layer with y=0.3 solid composition. The experimental PL emission energies at 10 K at different well thicknesses for the InAsyP1−y/InP SSQWs grown at 580 and 650 °C are in well agreement with the trend of the calculated curves. The TEM lattice image of an InAsP/InP SSQW grown at 580 °C on the order of two monolayers has been demonstrated. The InAsP/InP SSQW structure grown at 580 °C appears to be extremely abrupt, uniform, free of misfit dislocatio...

Liquid-phase epitaxial growth of InGaP for red electroluminescent devices

Abstract In this article we demonstrate the feasibility of growing n-AlGaAs/p-InGaP single heterostructures on a GaAs substrate by liquid-phase epitaxy. Good quality InGaP epitaxial layers as characterized by X-ray diffraction, Nomarski phase contrast microscope, photoluminescence and Hall measurements are obtained by optimizing the Ga liquid composition of 0.0093–0.0097 mole fraction in the InGaP growth solution. The minimum transition width of 200 A at the AlGaAsInGaP heterointerface is obtained by growing the AlGaAs epitaxial layer onto the as-grown InGaP layer with an 8°C supersaturation of AlGaAs growth solution. The p-n electrical junction is precisely controlled to be located at the metallurgical junction as measured by electron-beam induced current technique. Light-emitting diodes fabricated from the Al0.7Ga0.3As/In0.5Ga0.5P heterostructure have an emission peak wavelength of 660 nm. The forward-bias turn on voltage of 1.5 V with an ideality factor of 1.64 is obtained from the current-voltage measurements. The full-width at half-maximum of room-temperature electroluminescence and light output power at 100 mA of the uncoated red light-emitting diodes are 160 A and 400 μW, respectively. An external quantum efficiency of 0.3% is two-fold higher than those previously reported.

Interface abruptness and LED performance of the AlGaAs/InGaP single heterostructure grown by liquid-phase epitaxy

Selection of a proper supercooled temperature to grow an Al0.7Ga0.3As window layer onto an as-grown In0.5P active layer on a GaAs substrate has resulted in an improve device performance of Al0.7Ga0.3As/In0.5Ga0.5P single heterostructure light-emitting diodes. The transition width at the AlGaAs-InGaP interface is drastically reduced from 750 A to a minimum value of 200 A as the supercooled temperature of the AlGaAs melt was increased from 4 to 8°C. The light-emitting diode fabricated from this heterostructure shows a very small reverse leakage current of less than 1x10-6 A prior to breakdown and a forward-bias turn-on voltage of 1.50 V with an ideality factor of 1.64. The narrowest full width at half maximum of 160 A at 20 mA measured by room-temperature electroluminescent spectra and the strongest light output power of 400 μW at 100 mA are obtained when the AlGaAs layer was grown with this optimized supercooled temperature of 8°C. The external quantum efficiency of 0.3% is twice higher than that previously reported.