Ohmic electrode structure, semiconductor device including such ohmic electrode structure, and method for producing such semiconductor device

An ohmic electrode structure, comprising:

• an n-InxGa1-xAs layer, wherein x is greater than or equal to 0.5 and an impurity concentration of the n-InxGa1-xAs layer is greater than or equal to 2×1019 cm−3;
• a Pd layer provided on the n-InxGa1-xAs layer;
• and
• at least one metal layer provided on the Pd layer, wherein an ohmic contact is formed between the n-InxGa1-xAs layer and the Pd layer,
• the contact resistance of the Pd layer and the n-InxGa1-xAs layer being less than or greater than 1×10−6 Ωcm2.

A heterojunction bipolar transistor having an emitter-up structure including an emitter ohmic electrode structure and a base ohmic electrode structure, the emitter ohmic electrode structure comprising:

• an n-InxGa1-xAs layer, wherein x is greater than or equal to 0.5 and an impurity concentration of the n-InxGa1-xAs layer is greater than or equal to 2×1019 cm−3;
• a Pt layer provided on the n-InxGa1-xAs layer;
• and
• at least one metal layer provided on the Pt layer, wherein an ohmic contact formed between the n-InxGa1-xAs layer and the Pt layer, the contact resistance of the Pt layer and the n-InxGa1-xAs layer being less than or equal to 1×10−6 Ωcm2,
• the base ohmic electrode structure comprising:
• the Pt layer;
• and
• at least one metal layer provided on the Pt layer.

A heterojunction bipolar transistor having a collector-up structure including a collector ohmic electrode structure and a base ohmic electrode structure, the collector ohmic electrode structure comprising:

• an n-InxGa1-xAs layer where 0<x≦1;
• a Pt layer provided on the n-InxGa1-xAs layer;
• and
• at least one metal layer provided on the Pt layer;
• the base ohmic electrode structure comprising:
• the Pt layer;
• and
• at least one metal layer provided on the Pt layer.

A heterojunction bipolar transistor having an emitter-up structure including an emitter ohmic electrode structure and a base ohmic electrode structure, the emitter ohmic electrode structure comprising:

• an n-InxGa1-xAs layer, wherein x is greater than or equal to 0.5 and an impurity concentration of the n-InxGa1-xAs layer is greater than or equal to 2×1019 cm−3;
• a Pd layer provided on the n-InxGa1-xAs layer;
• and
• at least one metal layer provided on the Pd layer, wherein an ohmic contact is formed between the n-InxGa1-xAs layer and the Pd layer, the contact resistance of the Pd layer and the InxGa1-xAs layer being less than or equal to 1×10−6 Ωcm2;
• the base ohmic electrode structure comprising:
• the Pd layer;
• and
• at least more than one metal layer provided on the Pd layer.

A heterojunction bipolar transistor having a collector-up structure including a collector ohmic electrode structure and a base ohmic electrode structure, the collector ohmic electrode structure comprising:

• an n-InxGa1-xAs layer where 0<x≦1;
• a Pd layer provided on the n-InxGa1-xAs layer;
• and
• at least one metal layer provided on the Pd layer,
• the base ohmic electrode structure comprising:
• the Pd layer;
• and
• at least more than one metal layer provided on the Pd layer.