The performances of (InAs)1/(GaAs)2short-period superlattice strained single-quantum-well laser on GaAssubstrate

We fabricated an (InAs)₁/(GaAs)₂ short-period superlattice (SPS) strained quantum-well laser at 1.07 μm by MOVPE. The SPS active layer has 10 periods of (InAs)₁/(_GaAs)₂ and an average mismatch of over 2.2%. In highly strained conditions the device showed a lasing wavelength of 1.07 μm, a threshold of 130 A/cm², and a characteristic temperature T₀ of 175 K. We measured the gain characteristic by the Hakki and Paoli method at LED conditions and obtained a high differential gain of 2.0×10^-15 cm² at the threshold current     

10 A, 2.4 kV Power DiMOSFETs in 4H-SiC

We report the characteristics of large area (3.3 × 3.3 mm ²) high-voltage 4H-SiC DiMOSFETs. The MOSFETs show a peak MOS channel mobility of 22 cm²/V·s and a threshold voltage of 8.5 V at room temperature. The DiMOSFETs exhibit an on-resistance of 4.2 mΩ·cm² at room temperature and 85 mΩ·cm² at 200°C. Stable avalanche characteristics at approximately 2.4 kV are observed. An on-current of 10 A is measured on a 0.103 cm² device. High switching speed is also demonstrated. This suggests that the devices are capable of high-voltage, high-frequency, low-loss switching applications     

A fully planarized 4H-SiC trench MOS barrier Schottky (TMBS)rectifier

A fully planarized 4H-SiC trench MOS barrier Schottky (TMBS) rectifier has been designed, fabricated and characterized for the first time. The use of a TMBS structure helps improve the reverse leakage current by more than three orders of magnitude compared to that of a planar Schottky rectifier. We have achieved a low reverse leakage current density of 6×10^-6 A/cm² and a low forward voltage drop of 1.75 V at 60 A/cm² for the TMBS rectifier. The static current-voltage (I-V) and switching characteristics of the TMBS rectifier have been measured at various temperatures. A barrier height of 1.0 eV and an ideality factor of 1.8 were extracted from the forward characteristics. The switching characteristics do not change with temperature indicating the essential absence of stored charge     

Low-threshold strain-compensated InGaAs(N) (λ = 1.19-1.31μm) quantum-well lasers

Highly strained (Δa/a ~ 2.5%) In_0.4Ga_0.6 As and In_0.4Ga_0.6As_0.995N_0.005 -quantum-well (QW) active lasers utilizing strain-compensating InGaP-GaAsP buffer layers and GaAs_0.85P_0.15 barrier layers, grown by metal-organic chemical vapor deposition (MOCVD), are demonstrated with lasing emission wavelength of 1.185 and 1.307 μm, respectively. Threshold and transparency current density for the strain compensated InGaAsN QW lasers, with emission wavelength of 1.295 μm, are measured to be as low as 290 A/cm² (L = 1500 μm) and 110 A/cm², respectively, with characteristic temperature of T₀ and T₁ of 130 K and 400 K     

Low threshold current density operation of GaInP-AlGaInP visiblemultiple quantum wire-like lasers (MQWR-LDs) under the room temperaturepulsed condition

GaInP-AlGaInP multiple quantum wire-like layers were fabricated by the in situ strain induced lateral layer ordering process during MBE growth. According to TEM images, the quantum wire size was around 10 nm and quantum wire axis was along [011¯] direction. When we made laser diodes with stripes along [011] direction, the low threshold current density, of 315 A/cm² was obtained. Anisotropic lasing characteristics between [011] and [011¯] directions, in threshold current density, lasing mode, and lasing wavelength were observed     

Room-temperature operation of InAs quantum-dash lasers on InP (001)

The first self-assembled InAs quantum dash lasers grown by molecular beam epitaxy on InP (001) substrates are reported. Pulsed room-temperature operation demonstrates wavelengths from 1.60 to 1.66 μm for one-, three-, and five-stack designs, a threshold current density as low as 410 A/cm² for single-stack uncoated lasers, and a distinctly quantum-wire-like dependence of the threshold current on the laser cavity orientation. The maximal modal gains for lasing in the ground-state with the cavity perpendicular to the dash direction are determined to be 15 cm^-1 for single-stack and 22 cm^-1 for five-stack lasers     

Regenerative switching characteristics of a novel electrical oroptical base-controlled AlGaAs/GaAs quantum-well heterojunction bipolartransistor

A report is presented on the regenerative switching characteristics of a novel AlGaAs/GaAs quantum-well heterojunction bipolar transistor (QWHBT) with an electrically or optically controlled base grown by molecular beam epitaxy (MBE). This double-barrier QWHBT exhibits excellent electrical switching characteristics of 7 V and 0.03 A/cm² at the switching condition and 4.5 V and 3.2 A/cm² at the holding condition. When the device is operating as an optical switch, the optical base-controlled sensitivity is 6×10 ^-3 V/μW. The effects of temperature on the device performance were evaluated at 77 and 300 K. The results show that it may be used as an all-optical switch (flip-flop) for optical parallel image processing     

Interferometric measurement of the linewidth enhancement factor ofa 1.55-μm strained multiquantum-well InGaAs/InGaAsP amplifier

The linewidth enhancement factor of an InGaAs/InGaAsP strained multiquantum well optical amplifier was measured interferometrically. It varied from 3 to 18 over the wavelength range from 1500 to 1600 nm with injection currents varying from one to four times the lasing threshold of the uncoated device. A rate equation model gave differential gain and refractive index change per carrier, respectively, in the range 0.3 to 2.5×10^-15 cm² and -5 to -8×10^-20 cm³     

Room-temperature long-wavelength (λ=13.3 μm) unipolarquantum dot intersubband laser

Long-wavelength (λ=13.3 μm) unipolar lasing at 283 K from self-organised In_0.4Ga_0.6As/GaAs quantum dots, due to intersubband transitions in the conduction band, is demonstrated for the first time. The threshold current density under continuous wave operation is 1.1 kA/cm² for a 60 μm×1.2 mm broad-area plasmon-enhanced waveguide device and the maximum power output is ≈ μW. The long intersubband relaxation time in quantum dots, together with the short lifetime in the ground state, due to interband stimulated emission, help to achieve the necessary population inversion and gain     

Measurement of gain saturation coefficient of a DFB laser forlasing mode control by orthogonal polarization light

The frequency response of a 1.55-μm distributed feedback (DFB) laser is measured by injecting light which has an orthogonal polarization to the laser's lasing mode. The injected light, termed as orthogonal polarization light, is carefully selected to not couple to the lasing mode by adjusting its polarization to be orthogonal to that of the lasing mode and by setting its wavelength slightly different from that of the lasing mode. The wavelength of the orthogonal polarization light, however, is set within the range where the laser's active layer has a gain. The gain saturation coefficients for the lasing light are estimated to be 4.7×10^-23 cm² and that by the injected orthogonal polarization light (almost the same wavelength as the lasing mode) are 3.7×10^-23 cm², respectively     

Room-temperature pulsed operation of triple-quantum-well GaInNAslasers grown on misoriented GaAs substrates by MOCVD

The lasing operation of three-quantum-well GaInNAs stripe geometry lasers grown by MOCVD on 0° and 6° misoriented (100) GaAs substrates, respectively, have been demonstrated and their performance is compared for the first time. Both devices achieved room temperature, pulsed lasing operation at an emission wavelength of 1.17 μm, with a threshold current density of 667 A/cm² for lasers grown on 6° misoriented substrates, and 1 kA/cm² for lasers grown on 0° misoriented substrates. The threshold for the lasers grown on 6° misoriented substrates compares favorably with the best results for GaInNAs lasers. Lasers with narrower stripe width and a planar geometry have also been demonstrated by the use of lateral selective wet oxidation for current confinement, with a threshold current density of 800 A/cm² for 25-μm-wide devices     

Low-threshold continuous-wave two-stack quantum-dot laser withreduced temperature sensitivity

Data are presented on continuous wave operation of two-stack quantum dot lasers designed with reduced temperature sensitivity in their threshold. The InAs quantum dots are designed to have a wide energy spacing (~102 meV) between the ground and first excited radiative transitions. Selectively oxidized stripe lasers have continuous wave threshold currents as low as 1.2 mA for 2 μm wide stripes and minimum threshold current densities of 26 A/cm² for 13-μ-m wide stripes. Broad area lasers have continuous wave threshold current densities as low as 40 A/cm², even for p-up mounting. Ground state lasing is obtained up to the highest temperature measured of 326 K     

DC characteristics of high-breakdown-voltage p-i-n diodes made by20-MeV Si implantation in InP:Fe

A vertical p-i-n diode is made for the first time in InP:Fe using megaelectronvolt energy ion implantation, A 20-MeV Si implantation and kiloelectronvolt energy Be/P coimplantation are used to obtain a buried n⁺ layer and a shallow p⁺ layer, respectively. The junction area of the device is 2.3×10^-5 cm² and the intrinsic region thickness is ≈3 μm. The device has a high breakdown voltage of 110 V, reverse leakage current of 0.1 mA/cm² at -80 V, off-state capacitance of 2.2 nF/cm² at -20 V, and a DC incremental forward resistance of 4 Ω at 40 mA     

On-wafer continuous-wave operation of InGaN/GaN violet laser diodes

Continuous-wave operation of etched-facet InGaN/GaN multiquantum-well ridge-waveguide laser diodes grown by low pressure MOVPE on a sapphire substrate has been achieved on-wafer for >2 min at 15% above threshold. The threshold current density and voltage were 9.1 kA/cm² and 7.6 V, respectively, at 15°C, and the lasing wavelength was 400.6 nm     

Low threshold current density 1.3 μm metamorphic InGaAs/GaAs quantum well laser diodes

Very low threshold current density InGaAs/GaAs quantum well laser diodes grown by molecular beam epitaxy on InGaAs metamorphic buffers are reported. The lasing wavelength of the ridge waveguide laser diode with cavity length of 1200 mum is centered at 1337.2 nm; the threshold current density is 205 A/cm² at room temperature under continuous-wave operation.     

Very low threshold current density room temperature continuous-wavelasing from a single-layer InAs quantum-dot laser

Continuous-wave (CW) lasing operation with a very low threshold current density (J_th=32.5 A/cm²) has been achieved at room temperature by a ridge waveguide quantum-dot (QD) laser containing a single InAs QD layer embedded within a strained InGaAs quantum well (dot-in-well, or DWELL structure). Lasing proceeds via the QD ground state with an emission wavelength of 1.25 μm when the cavity length is longer than 4.2 mm. For a 5-mm long QD laser, CW lasing has been achieved at temperatures as high as 40°C, with a characteristic temperature T₀ of 41 K near room temperature. Lasers with a 20 μm stripe width have a differential slope efficiency of 32% and peak output power of >10 mW per facet (uncoated)     

High current density 800-V 4H-SiC gate turn-off thyristors

4H-SiC gate turn-off thyristors (GTOs) were fabricated using the recently developed inductively-coupled plasma (ICP) dry etching technique. DC and ac characterisation have been done to evaluate forward blocking voltage, leakage current, on-state voltage drop and switching performance. GTOs over 800 V dc blocking capability has been demonstrated with a blocking layer thickness of 7 μm. The dc on-state voltage drops of a typical device at 25 and 300°C were 4.5 and 3.6 V, respectively, for a current density of 1000 A/cm². The devices can be reliably turned on and turned off under an anode current density of 5000 A/cm² without observable degradation     

Optimum design conditions for AlGaAs window stripe lasers

The maximum available CW optical power from the AlGaAs window stripe laser was investigated both theoretically and experimentally. It is found that a thin third AlGaAs layer thickness and high-quality pulsed lasing characteristics, such as low threshold current density and high external differential quantum efficiency, which are obtained from refractive index guiding and short window-region length, are necessary to increase CW optical power. Stable fundamental lateral transverse mode CW operation was achieved at 55 mW (∼4.7 MW/cm²) in a window stripe (WS) laser with 3 μm stripewidth, which is about five times higher than the typical catastrophic optical damage (COD) threshold in conventional structure lasers. It was also found that a high-quality window stripe laser with 3 μm stripewidth operated at 30 mW (∼2.6 MW/cm²) for more than 3500 h.     

Lasing mode behavior of a single-mode MQW laser injected with TMpolarized light

The lasing mode behavior of a multiple quantum well (MQW) distributed feedback (DFB) laser was measured when intensity-modulated orthogonally polarized transverse magnetic (TM) mode light was injected. The 3-dB bandwidth of the frequency response shows a trend different from that observed with conventional bias current modulation: at high bias currents, it decreases with increasing bias current. The maximum bandwidth of 3 dB was observed when the normalized bias current was 4, and it reached 16 GHz at this bias current. The gain saturation coefficients for the transverse electric (TE) and TM modes estimated from these results were ∈_p^E; 2.5×10^-17 cm³ and ∈_q^E 5.7×10^-18 cm³ for the TE mode, and ∈_p^M: 6.0×10^-17 cm³ and ∈_q^M: 2.0×10^-14 cm³ for the TM mode     

High-performance long-wavelength (λ~1.3 μm) InGaAsPNquantum-well lasers

We demonstrate high-performance InGaAsPN quantum well based long-wavelength lasers grown on GaAs substrates, nitrogen containing lasers emitting in the λ=1.2- to 1.3-μm wavelength range were grown by gas source molecular beam epitaxy using a RF plasma nitrogen source. Under pulsed excitation, lasers emitting at λ=1.295 μm exhibited a record low threshold current density (J_TH) of 2. 5 kA/cm². Lasers grown with less nitrogen in the quantum well exhibited significantly lower threshold current densities of J_TH =1.9 kA/cm² at λ=1.27 μm and J_TH=1.27 kA/cm² at λ=1.2 μm. We also report a slope efficiency of 0.4 W/A and an output power of 450 mW under pulsed operation for nitrogen containing lasers emitting at 1.2 μm