Hf O 2 high-κ gate dielectrics on Ge (100) by atomic oxygen beam deposition

Abstract

Thin insulator films of the high-κ dielectric HfO2 are deposited on Ge(100) substrates by evaporating Hf in atomic oxygen beams after in situ thermal desorption of the native oxide in ultrahigh vacuum and subsequent treatment of the clean Ge surface in oxygen and nitrogen. It is shown that HfO2 forms atomically sharp interfaces with Ge and behaves as an excellent insulator with dielectric permittivity κ∼25, which is close to the expected bulk value. Very low equivalent oxide thickness of 0.75 (±0.1) nm with a low gate leakage current of ∼4.5×10−4A∕cm2 at 1 V in accumulation is achieved. Strong frequency dispersion of the inversion capacitance and low frequency behavior of the high frequency capacitance–voltage curves is observed. This is attributed to a combined effect of a high generation rate of minority carriers due to impurity traps and the high intrinsic carrier concentration in Ge, which result in a short minority carrier response time.

Metal-oxide-semiconductor devices with molecular beam epitaxy-grown Y2O3 on Ge

“…3(a)) has been achieved at a gate bias of V fb +1 V, which compares favorably with the previously measured leakage currents using MBE-Al 2 O 3 / Ga 2 O 3 (Gd 2 O 3 ) on Ge [11]. Compared to those with other commonly used dielectrics, such as GeO x N y [12], GeO x N y plus HfO 2 [1,[13][14][15], Si plus HfO 2 [16,17], and HfO 2 [18], several orders of reduction in leakage current density are attained in this work, as shown in Fig. 3(b), again indicating the excellence of the Al 2 O 3 / Y 2 O 3 and the Y 2 O 3 /Ge interface withstanding the 500 1C anneal.…”

Vacancy-oxygen defects in p-type Si1−xGex

“…[1][2][3][4][5] An enabling factor is the advent of high dielectric constant (high-k) dielectrics that allow the departure from the prerequisite to use native oxides such as SiO 2 in Si-based devices. [6][7][8] Si 1-x Ge x is a random alloy with the diamond structure that has one lattice site that can be occupied by either Si or Ge. The variation of its properties (such as band gap, electron and hole mobility, and lattice parameter) with respect to the Ge content is particularly important for microelectronic and optoelectronic devices.…”

Short minority carrier response time in HfO2 /Ge metal-insulator-semiconductor capacitors

“…Despite the progress, several issues related to the electrical characteristics of Ge MIS capacitors remain unresolved. The most puzzling effect is the low frequency behaviour of the highfrequency capacitance-voltage (C-V) curves, or more specifically, the observation of a high AC inversion capacitance [1][2][3][4] (close to the oxide capacitance value C ox ) at high frequencies (in the kHz range) which is not expected based on the experience we have with device quality Si. This behaviour is usually attributed to contamination [1,2] due to poor quality of bulk Ge starting material or due to insufficient surface passivation which creates high density of interface traps or mid-gap bulk semiconductor traps through metal diffusion from the high-overlayer.…”