III-V compound semiconductor heterostructure MOSFET device
View Patent ↗A III-V based, implant free MOS heterostructure field-effect transistor device comprises a gate insulator layer overlying a compound semiconductor substrate; ohmic contacts coupled to the compound semiconductor substrate proximate opposite sides of an active device region defined within the compound semiconductor substrate; and a gate metal contact electrode formed on the gate insulator layer in a region between the ohmic contacts. The ohmic contacts have portions thereof that overlap with portions of the gate insulator layer within the active device region. The overlapping portions ensure avoidance of an undesirable gap formation between an edge of the ohmic contact and a corresponding edge of the gate insulator layer.
1. A III-V based, implant free MOS heterostructure field-effect transistor device comprising:
a gate insulator layer overlying a compound semiconductor substrate, wherein the gate insulator layer/compound semiconductor interface comprises an annealed interface, the gate insulator layer/compound semiconductor interface having been annealed with a water vapor anneal to reduce a density of interface states (D it ) therein to a desired level;
ohmic contacts coupled to the compound semiconductor substrate proximate opposite sides of an active device region defined within the compound semiconductor substrate, the ohmic contacts having portions thereof that overlap with portions of the gate insulator layer within the active device region, the overlapping portions ensuring avoidance of an undesirable gap formation between an edge of the ohmic contact and a corresponding edge of the gate insulator layer; and
a gate metal contact electrode formed on the gate insulator layer in a region between the ohmic contacts, further comprising:
a protective layer overlying the gate insulator layer, wherein the ohmic contacts further include the ohmic contacts having a portion thereof that overlaps with the protective layer and the gate insulator layer, further wherein the gate metal contact electrode is formed through an opening in the protective layer at a desired location of the gate metal contact electrode, wherein the protective layer comprises an aluminum nitride (AlN) layer.
2. The device of claim 1 , wherein the desired level of density of interface states (D it ) is on the order of less than or equal to 5×10 11 cm −2 eV −1 .
3. The device of claim 1 , wherein AlN layer comprises a sputter deposited layer.
4. The device of claim 1 , further comprising:
one of a SiN or SiO layer disposed on the AlN protection layer.
5. The device of claim 1 , wherein the protective layer is configured for minimizing surface gettering of contaminants during storage, the protective layer also being configured for prevention of impurity diffusion into the insulator layer and towards an underlying insulator layer/compound semiconductor interface during a given temperature exposure.
6. The device of claim 1 , wherein the compound semiconductor substrate comprises a III-V substrate with one or more epitaxial layers thereon, further wherein the III-V substrate comprises one of GaAs or InP.
7. The device of claim 6 , further wherein the one or more epitaxial layers comprise any suitable layer structure of one or more of In, Ga, P, As, Sb, or Al containing compounds.
8. The device of claim 1 , wherein the insulator layer comprises a gate oxide layer.
9. The device of claim 8 , wherein the gate oxide layer comprises a high-k gate dielectric stack, the high-k gate dielectric stack providing low density of interface states (D it ) and low leakage, the low D it including a midgap at approximately 10 11 cm −2 eV −1 and the low leakage including a leakage current of approximately 10 nA/cm 2 at 1 MV/cm.
10. The device of claim 9 , wherein the high-k gate dielectric stack comprises a Gd x Ga 0.4-x O 0.6 /Ga 2 O 3 gate dielectric stack.
11. The device of claim 1 , wherein the gate insulator layer comprises a deposited gate oxide layer having a desired target thickness.
12. The device of claim 1 , further comprising isolation regions for defining the active device region, the isolation regions comprising one selected from the group consisting of isolation implant regions, shallow trench isolation regions, and mesa isolation regions.
13. The device of claim 1 , wherein the ohmic contacts comprise one or more of nickel (Ni), germanium (Ge), palladium (Pd), and gold (Au).
14. The device of claim 1 , wherein the gate metal contact electrode comprises a gate metallization that includes a high workfunction material of Pt or Ir for positive threshold voltages (V th ), the high work function gate metal contact electrode for enabling an enhancement mode operation.