Study of InGaP/InGaAs double doped channel heterostructure field-effect transistors (DDCHFETs)

Depletion-mode Al 0.24 Ga 0.76 As/In 0.22 Ga 0.78 As double-heterojunction high electron mobility transistors (DH-HEMTs) were fabricated with an as deposited gate to compare with those with a buried gate by annealing. Instead of a recessed gate, a buried gate used to control the distance between the gate and channel (and hence the aspect ratio) improves the series resistance. Measured transconductance of 150 mS mm −1 and an open-drain voltage gain of 136 for the DH-HEMT with an as deposited gate are enhanced to 175 mS mm −1 and 160 for the DH-HEMT with a 330 • C annealed gate. Good device linearity is also obtained with a low second harmonic to fundamental ratio of 3.55%. The measured maximums f t s ( f max s) are 13.5, 13.5 and 14.5 (35, 37, and 37.5) GHz for DH-HEMTs with an as deposited gate, and with 280 • C and 330 • C annealed gates, respectively. At a measured frequency of 2.4 GHz, the DH-HEMT with a 330 • C annealed gate exhibits the highest PAE = 44.8% at V DS = 3 V and V GS = −1.0 V and the lowest F min = 1.89 dB at V DS = 3 V and I D = 200 mA mm −1 .

Section: Resultsmentioning

confidence: 99%

“…The measured maximum f max s are 35, 37 and 37.5 GHz for devices A, B and C, respectively. The f t and f max seem relatively low but most likely this is due to the long gate length as in [6,[13][14][15]. However, all devices exhibit a f max /f t ratio of > 2.5 due to improved carrier confinement and low output conductance.…”

Section: Comparison Of Ac Performancementioning

confidence: 99%

Performance of Al_0.24Ga_0.76As/In_0.22Ga_0.78As double-heterojunction HEMTs with an as deposited and a buried gate

Chen¹,

Hsu²,

Chiu³

et al. 2006

“…However, conventional HEMT structures suffer from low gate-voltage swing (GVS), and thus the narrow constant transconductance versus the gatevoltage region restricts the digital applications to cellular/PCS phones. Recently, various channel structures have been proposed to solve this problem, such as doped channel [7][8][9], inversely graded channel [10,11] and symmetrically graded channel [13,14]. Doped-channel FETs exhibit good GVS and linearity but suffer from low electron mobility, which limits the high-frequency applications.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of In_0.52Al_0.48As/In_xGa₁₋_xAs/InP high-electron-mobility transistors with a symmetrically graded and an inversely graded channel

Huang

Hsu

Lin

et al. 2006

InP-based InAlAs/In x Ga 1−x As/InP high-electron-mobility transistors (HEMTs) with a symmetrically graded channel (SGC-HEMT) and an inversely graded channel (IGC-HEMT) were fabricated and studied. The SGC-HEMT exhibits better Hall, dc and RF characteristics than the IGC-HEMT because there are more electrons accumulated in the symmetrically graded channel. However, the IGC-HEMT has better thermal stability than the SGC-HEMT because the former has higher bandgap discontinuity at the channel/buffer heterojunction and less Coulomb scattering from a δ-doped layer. Furthermore, the IGC-HEMT sustains larger output power than the SGC-HEMT attributed to better breakdown characteristics. Therefore, HEMTs with the symmetrically graded and an inversely graded channel are suitable for high-speed and high-power applications, respectively.

“…The measured 2DEG concentration and mobility after removing the cap are 5.3 × 10 12 cm −2 and 6250 cm 2 V −1 s for the MDDFET at 300 K, respectively. The high 2DEG concentration is believed to be attributed to the large conduction band discontinuity between In 0.5 Al 0.5 As/In 0.5 Ga 0.5 As and the formation of In 0.5 Ga 0.5 As/δ + /In 0.5 Ga 0.5 As V-shaped quantum well [8]. The mobility is better than 4710 cm 2 V −1 s of the conventional InP-based In 0.5 Al 0.5 As/n + -In 0.5 Ga 0.5 As/In 0.5 Al 0.5 As DCFET attributed to the coupled wavefunction in the In 0.5 Ga 0.5 As / δ + /In 0.5 Ga 0.5 As/In 0.6 Ga 0.4 As/In 0.5 Ga 0.5 As/δ + / In 0.5 Ga 0.5 As channel [9].…”

Section: Resultsmentioning

confidence: 99%

A metamorphic heterostructure field-effect transistor with a double delta-doped channel

Huang

Hsu

Lin

et al. 2007

This study presents a metamorphic heterostructure field-effect transistor with a double δ-doped channel (MDDFET). The coupled δ-doped In 0.5 Ga 0.5 As/δ + /In 0.5 Ga 0.5 As/In 0.6 Ga 0.4 As/In 0.5 Ga 0.5 As/δ + /In 0.5 Ga 0.5 As channel demonstrates high carrier concentration and high mobility due to the good carrier confinement of the δ-doped design and the coupled wavefunction in the undoped In-rich channel. Experimental results indicate that the MDDFET with the gate dimension of 0.65 × 100 µm 2 exhibits a maximum extrinsic transconductance of 320 mS mm −1 , a saturated drain current density of 566 mA mm −1 at V GS = 0 V, a cut-off frequency of 45 GHz, a maximum oscillation frequency of 125 GHz and a saturated power of 15.9 dBm at 5.8 GHz. These results demonstrate that this studied device is appropriate for high-frequency and high-power applications.