Active solid-state devices (e.g. – transistors – solid-state diode – Heterojunction device – Field effect transistor
Patent
1994-02-14
1996-04-23
Jackson, Jr., Jerome
Active solid-state devices (e.g., transistors, solid-state diode
Heterojunction device
Field effect transistor
257194, H01L 29778
Patent
active
055106358
DESCRIPTION:
BRIEF SUMMARY
The invention relates to integrated circuits having complementary p-channel and n-channel field effect transistors.
Integrated circuits using complementary AlGaAs/GaAs heterojunction transistors (also called HIGFETs for "Heterojunction Insulated-Gate Field-Effect Transistors") are described by D .E. Grider et al. in Delta-Doped Complementary Heterostructure FETs with High Y-Value Pseudomorphic In.sub.y Ga.sub.1-y As Channels for Ultra-Low Power Digital IC Applications, IEDM Digest 1991, p. 235. In their work, D. E. Grider et al. have made 4-Kbit static random access memories (SRAM) having low electrical power consumption. More recently, they have improved their technology so as to further reduce the electrical power consumption of their integrated circuit (G. S. LaRue and D. E. Grider, Complementary HFET 32-bit Serial Multiplier, GaAs IC Symposium 92 Digest, p. 89).
The invention relates to that type of AlGaAs/GaInAs heterojunction type of component, and it seeks to mitigate a certain number of imperfections and limitations (explained in greater detail below) of known components that have already been proposed.
More precisely, an object of the present invention is to propose a suitable choice of thicknesses and of compositions for the epitaxial layers of such structures enabling complementary circuits to be implemented having very low electrical power consumption, while simultaneously increasing the transconductance of the p-channel transistor. That has not been possible until now because although an improvement in circuit power consumption has been achieved, there has been no improvement in the transconductance of the p-channel transistor. The reasons for these improvements are explained in detail below.
To this end, the component of the invention which is of the type comprising an integrated circuit having complementary components of the p-channel and n-channel field effect transistor type, with a heterojunction formed between a layer comprising an III-V semiconductor material having a wide forbidden band and a layer comprising an III-V semiconductor material having a narrow forbidden band and whose crystal lattice mismatch with the remainder of the structure is such that the layer comprising the narrow forbidden band material is under uniaxial compression strain in the plane of the layer, is characterized in that the thickness of the layer comprising the wide forbidden band material is selected to be smaller for the p-channel transistor than for the n-channel transistor, the ratio of these respective thicknesses being a predetermined ratio that is a function of the tunneling probability for holes compared with that for electrons.
In a first aspect of the invention, the heterojunction defines a quantum well including HH and LH type sub-bands in the valence band diagram of the heterostructure in the level that comprises the narrow forbidden band material, and the composition of the narrow forbidden band material is selected so that the energy differences between the sub-bands HH.sub.1, HH.sub.2 and LH.sub.1 is such that the population of the LH.sub.1 sub-band is essentially negligible and the gate leakage current of the p-channel transistor is essentially dependent of the low tunnel probability heavy holes HH.sub.1 and HH.sub.2.
In a second aspect of the invention, the thickness of the layer comprising the wide forbidden band material that is selected to be thinner for the p-channel transistor than for the n-channel transistor is further selected to as to reduce the absolute values of the threshold voltages of said transistors, thereby reducing the electrical power consumption of the circuit while increasing the transconductance of the p-channel transistor.
According to various advantageous characteristics or embodiments:
The material having a wide forbidden band is Al.sub.x Ga.sub.1-x As or (Al.sub.x Ga.sub.1-x).sub.u In.sub.1-u P and the material having the narrow forbidden band is Ga.sub.y In.sub.1-y As, said materials being grown epitaxially on a GaAs substrate.
The material having a wide forbidden ba
REFERENCES:
Kanji Yoh et al, "A p--channel GaSb heterojunction field--effect transistor based on a vertically . . . " Proceedings of the 18th Int'l Symposium on Gallium Arsenide & Related Compounds, Sep. 1991, pp. 173-178.
A. I. Akinwande et al., "Complementary III--V Heterostructure FETs for Low Power Integrated Circuits" Int'l Electron Devices Mtg., Dec. 1990, pp. 983-986.
S. R. Bahl et al., "Breakdown Voltage Enhancement from Channel Quantization in InAlAs
+--InGaAs HFET's", IEEE Electron Device Letters, vol. 13, No. 2, Feb. 1992, pp. 123-125.
Y--J Chan et al., "InAlAs/InxGa12--xAs HIGFET's (x>=0.53) for E/D FET Logic Applications", 3rd Int'l Conf. on Indium Phosphide & Related Materials, Apr. 1991, pp. 242-245.
S. Loualiche et al., "Influence of the Well Composition & Thickness in the GaInP/InP/GaInAs/InP Structure for HEMT", 3rd Int'l Conf. on Indium Phosphide & Related Materials, Apr. 1991, pp. 434-437.
Jackson, Jr. Jerome
Picogiga Societe Anonyme
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