Browsing by Author "Huang, JA"

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Au/Ge/Pd ohmic contacts to n-GaAs with the Mo/Ti diffusion barrier
(1996-12-01)
Chai, CY
;
Huang, JA
;
Lai, YL
;
Wu, JW
;
Chang, CY
The influences of the As-outdiffusion and Au-indiffusion on the performances of the Au/Ge/Pd/n-GaAs ohmic metallization systems are clarified by investigating three different types of barrier metal structures Au/Ge/Pd/GaAs, Au/Ti/Ge/Pd/GaAs, and Au/Mo/Ti/Ge/Pd/GaAs. The results indicate? that As-outdiffusion leads to higher specific contact resistivity, whereas Au-indiffusion contributes to the turnaround of the contact resistivity at even higher annealing temperature. For Au/Mo/Ti/Ge/Pd/n-GaAs samples, they exhibit the smoothest surface and the lowest specific contact resistivity with the wildest available annealing temperature,range, Moreover, Auger electron spectroscopy depth profiles show that the existing Ti oxide for the Mo/Ti bilayer can very effectively retard Au-indiffusion, reflecting the onset of the turnaround point at much higher annealing temperature.
Excellent Au/Ge/Pd ohmic contacts to n-type GaAs using Mo/Ti as the diffusion barrier
(1996-04-01)
Chai, CY
;
Huang, JA
;
Lai, YL
;
Wu, JW
;
Chang, CY
Au/Ge/Pd metallization system using Mo/Ti as the diffusion barrier between the Au overlayer and the Ge/Pd underlayer has been performed for the first time to achieve excellent ohmic contacts to n(+)-GaAs with the Si-doping concentration of about 2 x 10(18) cm(-3). The minimum specific contact resistivity as low as 1.2 x 10(-7) Ohm . cm(2) can be obtained after the rapid thermal annealing at 325 degrees C for 60 s, which is much lower than those of the conventional Au/Ge/Pd metallization systems. Furthermore, the available annealing temperature range for such low specific contact resistivities is also significantly extended from 325 degrees C to 400 degrees C. The improvement is attributed to the effective retardation of As-outdiffusion by the Mo/Ti barrier.
High-performance An/Ti/Ge/Pd ohmic contacts on n-Type In0.5Ga0.5P
(1996-04-01)
Chai, CY
;
Wu, JW
;
Guo, JD
;
Huang, JA
;
Lai, YL
High-performance Au/Ti/Ge/Pd ohmic contacts on n(+)-In0.5Ga0.5P have been fabricated for the first time. Using an n(+)-In0.5Ga0.5P epitaxial layer grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) with a Si dopant concentration of about 2 x 10(18) cm(-3), the minimum specific contact resistivity is as low as 1.2 x 10(-5) Ohm . cm(2), which is much lower than that of AuGeNi contacts after rapid thermal annealing at 400 degrees C for 60 s. The thermal stability of the Au/Ti/Ge/Pd system is significantly higher than that of conventional AuGeNi due to the introduction of the Ti barrier layer. Many holes and islands are observed on the surfaces of samples annealed at high temperature. The outdiffusion of P from the decomposed In0.5Ga0.5P substrate and agglomeration of Pd and Ge are the primary causes of contact degradation.
Mobility enhancements in AlGaN/GaN/SiC with stair-step and graded heterostructures
(1997-05-12)
Lin, CF
;
Cheng, HC
;
Huang, JA
;
Feng, MS
;
Guo, JD
In this letter, we report the observation of the enhanced electron mobility in three different Al0.08Ga0.92N/GaN heterostructures. These structures were deposited on (0001) 6H-SiC substrates by using the low-pressure metalorganic chemical vapor deposition method. The structure was composed of 500 Angstrom AlGaN compositional stair-step layer deposited onto 1.3 mu m GaN epitaxial layer. There is a 100 Angstrom GaN Cap layer on top of the AlGaN layer to prevent the oxidation of the AlGaN layer. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility for Al0.08Ga0.92N/GaN heterostructure are 6.6x10(12) cm(-2) and 5413 cm(2)/Vs at 77 K, respectively. This high value of mobility is, to the best of our knowledge, the first observed two-dimensional electron gas (2DEG) at the AlGaN/GaN stair-step type of heterostructure. Other interface structures such as graded composition and bulk composition structures were also prepared and 2DEG properties were observed. (C) 1997 American Institute of Physics.
Mobility enhancements in AlGaN/GaN/SiC with stair-step and graded heterostructures
(1997-05-12)
Lin, CF
;
Cheng, HC
;
Huang, JA
;
Feng, MS
;
Guo, JD
In this letter, we report the observation of the enhanced electron mobility in three different Al0.08Ga0.92N/GaN heterostructures. These structures were deposited on (0001) 6H-SiC substrates by using the low-pressure metalorganic chemical vapor deposition method. The structure was composed of 500 Angstrom AlGaN compositional stair-step layer deposited onto 1.3 mu m GaN epitaxial layer. There is a 100 Angstrom GaN Cap layer on top of the AlGaN layer to prevent the oxidation of the AlGaN layer. By using the van der Pauw method of Hall measurement, the sheet carrier density and mobility for Al0.08Ga0.92N/GaN heterostructure are 6.6x10(12) cm(-2) and 5413 cm(2)/Vs at 77 K, respectively. This high value of mobility is, to the best of our knowledge, the first observed two-dimensional electron gas (2DEG) at the AlGaN/GaN stair-step type of heterostructure. Other interface structures such as graded composition and bulk composition structures were also prepared and 2DEG properties were observed. (C) 1997 American Institute of Physics.