W. C. Hsu

In0.34Al0.66As0.85Sb0.15/δ(n+)-InP heterostructure field-effect transistors

A lattice-matched δ-doped In0.34Al0.66As0.85Sb0.15/InP heterostructure field-effect transistor (HFET) which provides large band gap (∼1.8 eV), high Schottky barrier height (φB>0.73 eV), and large conduction-band discontinuity (ΔEc>0.7 eV) has been proposed. In0.34Al0.66As0.85Sb0.15/InP heterostructures are shown to be type II heterojunctions with the staggered band lineup. This HFET demonstrates a output conductance of less than 1 mS/mm. Two-terminal gate-source breakdown voltage is more than 20 V with a leakage current as low as 170 μA at room temperature. High three-terminal off-state breakdown voltage as high as 36 V, and three-terminal on-state breakdown voltage as high as 18.6 V are achieved. The gate voltage swing is also significantly improved.

High breakdown voltage symmetric double δ-doped In0.49Ga0.51P/In0.25Ga0.75As/GaAs high electron mobility transistor

A double δ-doped In0.49Ga0.51P/In0.25Ga0.75As/GaAs high electron mobility transistor has been successfully fabricated by metalorganic chemical-vapor deposition. Improved electron mobility as high as 5410 (19 200) cm2/V s at 300 (77) K along with turn-on voltage as high as 2.3 V and reverse gate-to-drain voltage up to 75 V are achieved. These characteristics are attributed to the use of the δ-doped, undoped InGaP Schottky layer, and undoped GaAs setback layer. Moreover, the parasitic parallel conduction can be eliminated. The activation energy is also deduced.

Variation of the mobility and the two‐dimensional electron gas concentration with indium composition in δ‐doped GaAs/InxGa1−xAs/GaAs pseudomorphic structures

The electron mobility and the two‐dimensional electron gas (2DEG) concentration in different indium compositions (0.1<x<0.6) δ‐doped GaAs/InxGa1−xAs/GaAs pseudomorphic structures grown by low‐pressure metalorganic chemical vapor deposition are studied. The electron mobilities of a δ‐doped GaAs layer are comparable to those of previous reports. Furthermore, the maximum mobility (5500 and 33 000 cm2/V s at 300 and 77 K, respectively) of the proposed pseudomorphic structure appears at x=0.37. Taking into account of strain and quantum effects, the variation trends of calculated 2DEG concentrations are in good agreement with the experimental results.

Mobility enhancement in double δ‐doped GaAs/InxGa1−xAs/GaAs pseudomorphic structures by grading the heterointerfaces

A novel double δ‐doped heterostructure employing symmetric graded InGaAs quantum wells as the active channel grown by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) has been successfully fabricated. The proposed symmetrically graded InGaAs pseudomorphic structure manifests significantly improved electron mobility as high as 5300 (26 000) cm2/V s at 300 (77) K due to superior confinement and to the lower interface roughness scattering at GaAs/InGaAs heterointerfaces. We also carried out photoluminescence (PL) spectra and secondary‐ion mass spectrometry (SIMS) profiles to confirm the quality of the proposed structures.

Characteristics of a δ ‐doped GaAs/InGaAs p‐channel heterostructure field‐effect transistor

A δ‐doped GaAs/In0.2Ga0.8As p‐channel heterostructure field‐effect transistor grown by low‐pressure metalorganic chemical vapor deposition is demonstrated. The mobilities and two‐dimensional hole gas concentrations at 300 (77) K are 260 (2600) cm2/v s and 1012 (5.5×1011) cm−2, respectively. For a gate length of 1.5 μm, the maximum extrinsic transconductances are 15 mS/mm at 300 K and 24 mS/mm at 77 K. The high transconductances extend a wide range versus gate voltage.

Very strong negative differential resistance real‐space transfer transistor using a multiple δ‐doping GaAs/InGaAs pseudomorphic heterostructure

We present the observation of an effective real‐space transfer process of hot electrons resulting in a very strong negative differential resistance in GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructure by growing symmetrically double δ‐doping layers on both sides of the InGaAs channel. By Hall measurements, the proposed structure shows carrier mobility as high as 4500 (14 100) cm2/V s at 300 (77) K which is suitable for high‐frequency operations. Meanwhile, this structure with a 5×100 μm2 emitter channel reveals extremely sharp charge injection, broad current valley range (≳3 V), high transconductance (over 23.5 S/mm), high current driving capability, and high peak‐to‐valley current ratio (up to 156 000). We also carried out secondary‐ion mass spectrometry profiles to confirm the quality of the proposed structure.

Characteristics of graded‐like multiple‐delta‐doped GaAs field effect transistors

Multiple‐δ‐doped GaAs field effect transistors using graded‐like δ‐doping profile are demonstrated and investigated. An extremely high carrier density of 1.2×1013 (7.9×1012) cm−2 along with an enhanced Hall mobility of 1700 (3300) cm2/v s at 300 (77) K for a triple‐δ‐doped GaAs structure are achieved. The dc characteristic reveals an extrinsic transconductance as high as 110 mS/mm at room temperature with a gate length of 2 μm. Three separated peaks in the transconductance versus gate bias curve are observed. Meanwhile, a broad and flat transconductance region is obtained.

Improved mobilities and concentrations in double quantum well InGaAsGaAs pseudomorphic HFETs using multi-coupled δ-doped GaAs

Abstract In this work, we report the improvement of mobilities and concentrations using multi-coupled Si-°-doped GaAs layers in double quantum well (DQW) GaAs/InGaAs/GaAs pseudomorphic hetero-structures. The improved mobilities and sheet carrier densities are 5200 (21,000) cm2/Vs and 7.6 (5.0) × 1012 cm−2 at 300 (77) K, respectively, which are significantly superior to those of single quantum well structures. The transconductance and saturation current density are as high as 240 mS/mm and 750 mA/mm, respectively, at 300 K with a gate length of 1.5 μm.

Electrical characteristics of a lattice-matched In0.53Al0.22Ga0.25AsInP heterojunction bipolar transistor with zero potential spike at emitter-base heterojunction

Abstract We report qualitatively a lattice-matched In 0.53 Al 0.22 Ga 0.25 As InP heterojunction bipolar transistor grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The In 0.53 Al 0.22 Ga 0.25 As InP heterostructure has a large valence band discontinuity and a zero conduction band discontinuity which are suitable for the HBTs. A common-emitter current gain of 85 along with a low offset voltage 50 mV are obtained. The junction ideality factors of collector and base current are 1.18 and 1.35, respectively. The current gain ( h FE ) slightly increases with the increase of collector current.

Secondary‐ion mass spectrometry analysis in pseudomorphic GaAs/InGaAs/GaAs heterostructures utilizing a δ‐doping superlattice

Significant improvement on two‐dimensional electron gas (2DEG) concentration and mobility in a δ‐doping superlattice GaAs/In0.25Ga0.75As/GaAs pseudomorphic heterostructures prepared by low‐pressure metalorganic chemical vapor deposition have been demonstrated and discussed. The secondary‐ion mass spectrometry profiles of these δ‐doping superlattice structures were studied. The triple and double δ‐doping superlattice heterostructures showed extremely high 2DEG concentrations of 8.8 (6.0) and 4.3 (2.5)×1012 cm−2 along with enhanced mobilities of 2710 (6500) and 3916 (18400) cm2/V s at 300 (77) K, respectively. The 2DEG concentrations, to our knowledge, are among the highest for previously reported pseudomorphic heterostructures with similar mobilities.