Emitter contact epitaxial structure and ohmic contact formation for heterojunction bipolar transistor
Embodiments of the present disclosure describe apparatuses, methods, and systems of an integrated circuit (IC) device. The IC device includes a diffusion control layer as part of an emitter epitaxial structure. The IC device may utilize a common metallization scheme to simultaneously form an emitter contact and a base contact. Other embodiments may also be described and/or claimed.
1. An apparatus comprising:
a gallium arsenide (GaAs) base layer;
an indium gallium phosphide (InGaP) emitter layer formed on the GaAs base layer;
an emitter epitaxial structure formed on the InGaP emitter layer, including:
an indium gallium arsenide (InGaAs) layer; and
a diffusion control layer formed on the InGaAs layer;
a base contact coupled with at least one of the GaAs base layer or the InGaP emitter layer; and
an emitter contact coupled with the diffusion control layer, wherein the diffusion control layer comprises a super lattice structure having alternating layers of a first material and a second material.
2. The apparatus of claim 1 , wherein the base contact and the emitter contact have a common metallization structure.
3. The apparatus of claim 2 , wherein the common metallization structure comprises:
a first platinum (Pt) layer;
a titanium (Ti) layer formed on the first Pt layer;
a second Pt layer formed the on the Ti layer; and
a gold (Au) layer formed on the second Pt layer.
4. The apparatus of claim 3 , wherein the first Pt layer of the emitter contact extends through the diffusion control layer and partially into the InGaAs layer.
5. The apparatus of claim 1 , wherein the diffusion control layer comprises at least one of InGaP, GaAs, indium phosphide (InP), indium aluminum arsenide (InAlAs), aluminum gallium arsenide (AlGaAs), or InGaAs.
6. The apparatus of claim 5 , wherein the diffusion control layer is an InGaP layer having a thickness of approximately 300 to 500 angstroms.
7. The apparatus of claim 5 , wherein the diffusion control layer is an InGaP layer having a thickness approximately equal to a thickness of the InGaP emitter layer.
8. The apparatus of claim 1 , wherein the first material is InGaAs and the second material is one of GaAs, indium phosphide (InP), indium aluminum arsenide (InAlAs), InGaP or aluminum gallium arsenide (AlGaAs).
9. The apparatus of claim 1 , wherein the super lattice structure contains at least three periods, each period comprising a layer of the first material having a thickness of between approximately 20-100 angstroms and a layer of the second material having a thickness of between approximately 20-100 angstroms.
10. The apparatus of claim 1 , wherein the emitter epitaxial structure further comprises:
a GaAs layer formed on the InGaP emitter layer; and
a graded InGaAs layer formed on the GaAs layer,
wherein the InGaAs layer is formed on the graded InGaAs layer.
11. A system comprising:
a transceiver to transmit and receive radio frequency (RF) signals; and
a heterojunction bipolar transistor (HBT) incorporated within or coupled with the transceiver, the HBT including:
a gallium arsenide (GaAs) base layer;
an indium gallium phosphide (InGaP) emitter layer formed on the GaAs base layer;
an emitter epitaxial structure formed on the InGaP emitter layer, comprising:
an indium gallium arsenide (InGaAs) layer; and
a diffusion control layer formed on the InGaAs layer;
a base contact coupled with at least one of the GaAs base layer or the InGaP emitter layer; and
an emitter contact coupled with diffusion control layer, wherein the diffusion control layer comprises a super lattice structure having alternating layers of a first material and a second material.
12. The system of claim 11 , further comprising at least one of a power amplifier or a power condition, wherein the at least one of a power amplifier or a power condition includes the HBT.