High-performance p-channel thin-film transistors with lightly doped n-type excimer-laser-crystallized germanium films

Abstract

High-performance polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) fabricated with lightly doped Ge thin films by excimer laser crystallization (ELC) and counter doping (CD) have been demonstrated. High-quality n-type Ge thin films with a grain size as large as 1 µm were fabricated by ELC in the super lateral-growth regime and CD at a dose of 1 × 1013 cm−2 or higher. Consequently, a superior field-effect mobility of 271 cm2 V−1 s−1 and a high on/off current ratio of 2.7 × 103 have been obtained for p-channel Ge TFTs with the channel width and length of both 0.5 µm fabricated by ELC at 300 mJ/cm2 and CD at a dose of 1 × 1013 cm−2. The effects of ELC conditions and CD dose on the electrical characteristics of p-channel Ge TFTs were also investigated.

Improving carrier mobility of polycrystalline Ge by Sn doping

“…Many crystallization techniques have been developed, including solid-phase crystallization (SPC) 14 – 16 , laser annealing 17 , 18 , chemical vapor deposition 19 , 20 , flash-lamp annealing 21 , the seed layer technique 22 , and metal-induced crystallization 23 – 25 . By using these techniques, Ge-TFTs have been fabricated on thermally oxidized Si 21 , 26 , 27 , glass 28 – 31 , and even flexible substrates 22 , 32 . Since gate stack technology for Ge has developed sufficiently 8 , recent Ge-TFTs performance is limited by the properties of the poly-Ge thin film itself 21 , 22 , 26 – 32 .…”

“…By using these techniques, Ge-TFTs have been fabricated on thermally oxidized Si 21 , 26 , 27 , glass 28 – 31 , and even flexible substrates 22 , 32 . Since gate stack technology for Ge has developed sufficiently 8 , recent Ge-TFTs performance is limited by the properties of the poly-Ge thin film itself 21 , 22 , 26 – 32 . Some of these TFTs exhibited effective hole mobilities greater than 100 cm 2 /V s 22 , 26 , 28 .…”

“…Since gate stack technology for Ge has developed sufficiently 8 , recent Ge-TFTs performance is limited by the properties of the poly-Ge thin film itself 21 , 22 , 26 – 32 . Some of these TFTs exhibited effective hole mobilities greater than 100 cm 2 /V s 22 , 26 , 28 . This value is equivalent to the effective mobility of bulk-Si p-MOSFETs; however, much lower than that of bulk-Ge p-MOSFETs 7 , 8 .…”

Sb-doped crystallization of densified precursor for n-type polycrystalline Ge on an insulator with high carrier mobility

“…[4][5][6][7][8] The most promising usage of such high-performance Ge-CMOS is to integrate it into Si large-scale integrated circuits (LSIs) or flat-panel displays. To achieve this, low-temperature Ge-on-insulator (GOI) technology has been developed, including solid-phase crystallization (SPC), [9][10][11][12][13] laser annealing, [14][15][16][17][18] chemical vapor deposition, 19,20 flash-lamp annealing, 21 the seed layer technique, 22 and metal-induced crystallization. [23][24][25][26][27] Using the resulting polycrystalline (poly-) Ge layers, p/n-channel MOSFETs 12,13,17,21,27 and even CMOS operation have been successfully demonstrated.…”

Advanced solid-phase crystallization for high-hole mobility (450 cm2V−1s−1) Ge thin film on insulator

“…[13][14][15][16] Although these techniques are attractive for achieving high-quality GOIs, the direct low-temperature formation (<600 °C) of Ge on arbitrary substrates is desired for lowering the process costs and expanding the device application. Polycrystalline Ge (poly-Ge) thin films have been directly formed on glass or plastic substrates at low temperatures using solid-phase crystallization (SPC), [17][18][19][20][21][22] laser annealing, [23][24][25][26] chemical vapor deposition, 27,28) flash lamp annealing, 29) and metalinduced crystallization. [30][31][32][33][34] However, the performance of the Ge thin-film transistors (TFTs) has been no match for that of Si-MOSFETs.…”