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Wu H.-M.,National Taiwan University | Tsai S.-J.,Visual Photonics Epitaxy Company | Chang Y.-C.,National Taiwan University | Chen Y.-R.,National Taiwan University | Lin H.-H.,National Taiwan University
Thin Solid Films | Year: 2014

We report on the structural properties of ordering InGaP directly deposited on (001) Ge substrate by organometallic vapor phase epitaxy. The Ge substrate is 6° miscut towards (110). Results from transmission electron diffraction indicate the existence of CuPt-B ordering phase in the sample. The ordering direction is assigned to be [11¯1], which is perpendicular to the miscut direction of the Ge substrate. Because only one ordering phase is observed, no anti-phase domain exists in the sample. The order parameter determined from photoluminescence at room temperature is 0.492. Raman scattering was also used to analyze the ordering effect. A mode at 354 cm- 1 relevant to the ordering phase confirms that the CuPt-B ordering is along [11¯1]. © 2014 Elsevier B.V.


Wu H.-M.,National Taiwan University | Tsai S.-J.,Visual Photonics Epitaxy Company | Ho H.-I.,National Taiwan University | Lin H.-H.,National Taiwan University
Journal of Applied Physics | Year: 2016

We report on the Ge auto-doping and out-diffusion in InGaP epilayer with Cu-Pt ordering grown on 4-in. Ge substrate. Ge profiles determined from secondary ion mass spectrometry indicate that the Ge out-diffusion depth is within 100 nm. However, the edge of the wafer suffers from stronger Ge gas-phase auto-doping than the center, leading to ordering deterioration in the InGaP epilayer. In the edge, we observed a residual Cu-Pt ordering layer left beneath the surface, suggesting that the ordering deterioration takes place after the deposition rather than during the deposition and In/Ga inter-diffusion enhanced by Ge vapor-phase auto-doping is responsible for the deterioration. We thus propose a di-vacancy diffusion model, in which the amphoteric Ge increases the di-vacancy density, resulting in a Ge density dependent diffusion. In the model, the In/Ga inter-diffusion and Ge out-diffusion are realized by the random hopping of In/Ga host atoms and Ge atoms to di-vacancies, respectively. Simulation based on this model well fits the Ge out-diffusion profiles, suggesting its validity. By comparing the Ge diffusion coefficient obtained from the fitting and the characteristic time constant of ordering deterioration estimated from the residual ordering layer, we found that the hopping rates of Ge and the host atoms are in the same order of magnitude, indicating that di-vacancies are bound in the vicinity of Ge atoms. © 2016 AIP Publishing LLC.


Chin Y.-C.,National Taiwan University | Lin H.-H.,National Taiwan University | Huang C.-H.,Visual Photonics Epitaxy Company
IEEE Electron Device Letters | Year: 2012

We report on the dc characteristics of an InGaP GaAs 0.57P 0.28Sb 0.15GaAs double heterojunction bipolar transistor (DHBT). In comparison with control InGaP/GaAs single heterojunction bipolar transistors (SHBTs), the DHBT shows a lower turn-on voltage V BE on by ∼70 mV, a lower knee voltage up to J c∼40 kA 2, and less temperature-sensitive current gain. The validity of reciprocity in the Gummel plot suggests no potential spikes at the emitter/base and base/collector (BC) junctions of the DHBT. By considering the differences, in terms of the built-in voltage of the BC junction, the Fermi level in the base, and the renormalized energy gap of the base, between the GaAsPSb DHBT and the control InGaP/GaAs SHBT, we conclude that the heavily p-doped GaAs 0.57P 0.28Sb 0.15 base and the lightly n-doped GaAs collector are in weakly type-II band alignment with a conduction and valence band offset of 44 and 221 meV, respectively. These findings indicate that GaAsPSb is a promising base material for DHBTs operating at high temperature and low V BE, on conditions without suffering from the collector current blocking. © 2012 IEEE.


Patent
Visual Photonics Epitaxy Co. | Date: 2015-05-15

Provided is a heterojunction bipolar transistor (HBT), including a GaAs substrate; a subcollector layer stacked on the GaAs substrate, wherein a part of or all of the subcollector layer is formed by N-type group III-V semiconductors doped by at least Te and/or Se; a blocking layer structure directly or indirectly stacked on the subcollector layer, and formed by N-type group III-V semiconductors doped by at least group IV elements, a collector layer stacked on the blocking layer structure, and formed by N-type group III-V semiconductors; a base layer stacked on the collector layer, and formed by P-type group III-V semiconductors; an emitter layer stacked on the base layer and formed by N-type group III-V semiconductors; an emitter cap layer stacked on the emitter layer and formed by N-type group III-V semiconductors; and an ohmic contact layer stacked on the emitter cap layer and formed by N-type group III-V semiconductors.


Patent
Visual Photonics Epitaxy Co. | Date: 2014-11-07

A directed epitaxial heterojunction bipolar transistor (HBT) structure is directly or indirectly formed on a GaAs substrate that is formed by a (100) face towards a (111)B face with an angle of inclination between 0.6 and 25, and includes a sub-collector layer, a collector, a base layer, an emitter layer, an emitter cap layer and an ohmic contact layer, which are sequentially formed on the substrate. A tunnel collector layer formed by InGaP or InGaAsP is provided between the collector layer and the base layer. Since an epitaxial process is performed on the substrate from a (100) face towards a (111)B face with an angle of inclination between 0.6 and 25, indium and gallium contained in InGaP or InGaAsP are affected by the ordering effect such that InGaP or InGaAsP used in the emitter layer and/or the tunnel collector layer has a higher electron affinity or a smaller bandgap.

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