Monday, January 4, 2010

Towards a germanium-based CMOS technology

From Semiconductor International: "MIRAI Advances Ge Transistor Prototype"

The prototype is produced on a bulk germanium material, but later the transistor will be fabricated with a Ge-on-Si substrate. In the early days of the semiconductor industry, germanium was replaced by silicon partly because germanium lacked a stable native oxide, a challenge now being resolved by the introduction of high-k dielectrics. Also, the early germanium transistors could not withstand high-temperature operations because of the lower energy bandgap, which is being resolved in part by the use of strain techniques.

The attraction of germanium is its higher mobility of 4000-5500 cm2/Vsec, depending on the amount of strain, which is almost triple the electron mobility of silicon. According to a calculation by MIRAI engineers, the electron mobility increases as the energy bandgap decreases, which allows strain to impact the germanium bandgap.

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