AlGaAs/InGaAs pseudomorphic high electron mobility transistor using Pd/Ge ohmic contact

J. L. Lee, Y. T. Kim, J. W. Oh, B. T. Lee

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6 Citations (Scopus)


Microstructural reactions of a Pd/Ge contact to a AlGaAs/InGaAs pseudomorphic high electron mobility transistor (PHEMT) have been investigated, and the results have been used to interpret the changes of electrical properties of the PHEMT. In the as-deposited state, a ternary phase of PdxGaAs containing excess Ge atoms is formed at the interface of Pd/GaAs. When the ohmic metals deposited were annealed at 300°C, a PdGe compound was formed and its contact resistivity was decreased to 1.2 × 10-7 Ω·cm2. This is due to the preferential outdiffusion of Ga atoms to the PdGe during annealing, leaving Ga vacancies behind. Simultaneously, Ge atoms are indiffused to the GaAs and occupy the Ga vacancies, converting the interfacial GaAs layer into n+-GaAs. The low-temperature PdGe ohmic contact allows changing the sequence in the formation of source/drain and gate electrodes in the PHEMT process. The device performance was remarkably improved as the annealing temperature was increased or the contact resistivity was reduced. The PHEMTs with a gate length of 1.1μm, annealed at 300°C, exhibit maximum transconductance of 381 mS/mm.

Original languageEnglish
Pages (from-to)1188-1193
Number of pages6
JournalJapanese Journal of Applied Physics
Issue number3 A
Publication statusPublished - 2001 Mar

All Science Journal Classification (ASJC) codes

  • General Engineering
  • General Physics and Astronomy


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