Analytical calculation of the quantum 1/f coherence parameter for HFETs

Peter H. Handel; Taher S. Sherif

doi:10.1117/12.842972

17 March 2010 Analytical calculation of the quantum 1/f coherence parameter for HFETs

Peter H. Handel, Taher S. Sherif

Proceedings Volume 7602, Gallium Nitride Materials and Devices V; 76020N (2010) https://doi.org/10.1117/12.842972
Event: SPIE OPTO, 2010, San Francisco, California, United States

Abstract

The ratio s of the coherent magnetic energy term and the incoherent mechanical kinetic energy terms of the drift motion in the hamiltonian of a current carrying system is calculated for the special cases of a HFET or FET. This ratio defines the resulting quantum 1/f noise from the coherent and conventional quantum 1/f effects. In this case of FETs and HFETs of much larger width w>>L_DS>t, the kinetic energy E_k of average motion with drift velocity v_d per unit length in the direction of the drain-source distance L_DS in the channel of thickness t, is still given by Nmv_d ²/2, but the magnetic energy E_m per unit length in the direction of L_DS is roughly proportional with the first power of w only, instead of w², and can be approximated by E_m = π[ln(w/2L_DS)]L_DS[nevS/c]²/w. Here S=wt is the cross section though which current flows this indicates field-decoherence along the large device width w. This yields a coherence ratio of s ≡ E_m/E_k ≈ πnr_otL_DSln(w/2L_DS), which shows that only an effective width w=w_eff about equal to L_DS should be used in the calculation of s in this special case; larger widths are subject to de-coherence. This favors lower, mainly conventional, quantum 1/f noise in these devices, in spite of the large values of w. It also explains for the first time why the huge widths are possible with impunity, i.e., without causing the much larger coherent quantum 1/f noise to appear. For non-uniform current distribution across t, and for piezoelectric coupling, improved forms are derived for s. Specifically, the coherence parameter, called s' for the piezo case, is given by s' = (gN'h/m^*v_s)( v_s/u)³F(u/v_s)t/12w, where F(u/v_s) = (2/3)(u/v_s) for small drift velocity u, much smaller than the sound velocity v_s in the semiconductor. Here N'=nwt.

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Peter H. Handel and Taher S. Sherif "Analytical calculation of the quantum 1/f coherence parameter for HFETs", Proc. SPIE 7602, Gallium Nitride Materials and Devices V, 76020N (17 March 2010); https://doi.org/10.1117/12.842972

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KEYWORDS

Magnetism

Field effect transistors

Semiconductors

Particles

Gallium nitride

Infrared radiation

Phonons

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