JP2643546B2 - Manufacturing method of heterojunction bipolar transistor using germanium and gallium arsenide - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a heterojunction bipolar transistor (HBT) using germanium and gallium arsenide.

(Prior Art) As a conventional example of a heterojunction bipolar transistor using germanium and gallium arsenide, for example, the document “Forty Sevens Annual Devices Research Conference” (47th Annual) by Kimura (the inventor of the present invention) et al. Device Research Conference) II A
No. -8 describes a bipolar transistor using a heterojunction of germanium (hereinafter Ge) and gallium arsenide (GaAs) as an ultra-high-speed, low-power-consumption device. Ge and GaAs
Molecular beam epitaxy (MBE) was used to fabricate the heterojunction, and Ge molecular beams were generated using an electron gun.

(Problems to be Solved by the Invention) The conventional method using the electron gun (E-gun) growth method for growing Ge on GaAs can provide a practical value of several μm / hour as the Ge growth rate. N with good characteristics
-GaAs / p-Ge diode can be manufactured. However, when antimony (Sb) is used as a dopant when fabricating n-type Ge serving as a collector, the doping concentration is 1 × 10
The leakage current between the base and the collector made of a p-Ge / n-Ge diode is as small as ¹⁶ cm ^-3 or less. Also, when arsenic (As) is used, there is a disadvantage that the controllability of the concentration is poor and a collector layer cannot be formed. In the method using Knudsen cell (K-cell) for growing Ge, a good quality n-type
Although Ge can be obtained and a base / collector junction without leakage current can be produced, the cell is usually composed of boron nitride, and the temperature at which decomposition of boron nitride starts is 1250 ° C.
Since the heating cannot be performed any more, the growth rate is on the order of several thousand angstroms / hour. Applied Physics Letters, No. 5 by Djula-Eres et al.
As shown in Vol. 5, No. 9, p. 858, when the growth rate of Ge is slow, high concentration of donor and asceptor in Ge layer near the interface with GaAs layer by auto-doping of Ga and As atoms from GaAs layer. It is considered that the characteristics of the n-GaAs / p-Ge diode are deteriorated.

(Means for Solving the Problems) The present invention relates to a method of manufacturing an npn-type heterojunction bipolar transistor in which germanium as a base and a collector layer is formed on gallium arsenide as an emitter layer.
Manufacturing of a heterojunction bipolar transistor characterized in that germanium in contact with the emitter layer of the base layer uses molecular beam epitaxial growth using an electron gun, and germanium in contact with the collector layer uses molecular beam epitaxial growth using a Knudsen cell. Is the way.

(Operation) Hereinafter, the operation of the present invention will be described with reference to the drawings based on data obtained as a result of an experiment by the present inventors. Figure 2 shows a conventional
It is a structural diagram of Ge / GaAsHBT. As the emitter layer 8, n doped with Si so as to have a carrier concentration of 1 × 10 ¹⁷ cm ^−3.
Ge is grown on the GaAs layer 8 at a growth rate of 2 .mu.m / hour by 1000.degree. By an electron gun growth method to form a p-type base layer 9, which is then doped with Sb by an ionized Knudsen cell and then similarly grown by an electron gun growth method. The n-type collector layer 10 is formed by growing Ge by 5000 °. Figure 3 made
It is a common emitter current-voltage characteristic of HBT. Collector current (L _C ) against emitter-collector voltage (V _EC ) application
Does not show saturation. 4 (a) and 4 (b) show the emitter-base current-voltage characteristics and the base-base current characteristics of this device, respectively.
This is a current-voltage characteristic between collectors. FIG. 4 (a) shows that the characteristics of the emitter-base junction are good.
It can be seen from (b) that a leakage current is generated when a reverse voltage is applied to the Ge pn junction diode serving as the base and collector. FIGS. 5 (a) and 5 (b) show 0.2 μm
4 shows current-voltage characteristics between an emitter and a base and between a base and a collector of an HBT grown using a K-cell at a growth rate of / hour. 4 (a) and 4 (b), the reverse leakage current between the base and the collector is small, but in this case, the reverse leakage current between the emitter and the base increases, and the ideal in the forward direction. The count is much greater than one. From these results, (1) n-type GaAs / p-type G constituting the emitter / base of HBT
The characteristic of the e-diode is preferably a method using an electron gun growth method and using a germanium growth method with a growth rate of several μm / hour.

(2) p-type Ge / n-type Ge forming the base collector of HBT
Diode characteristics are better when using a Knudsen cell growth method with a growth rate of several thousand angstroms / hour.

You can see that. Therefore, GaAs is the emitter, Ge is the base,
When manufacturing an npn-type HBT used as a collector, the base and collector are formed on GaAs as the emitter using the MBE method.
At the time of growing Ge, the growth rate of Ge is initially set to several μm / hour by using an electron gun growth method, and then to several thousand angstroms by K-cell growth method. An ideal Ge / GaAs HBT can be manufactured by growing Ge on GaAs using the / h growth method.

FIG. 1 is a structural view of a Ge / GaAs HBT according to an embodiment of the present invention. An emitter layer 1 is formed on n-type GaAs doped with Si so as to have a carrier concentration of 1 × 10 ¹⁷ cm ^-3.
A 500 ° Ge layer 2 is grown at a growth rate of m / hour by an electron gun growth method, and then a 500 ° Ge layer 3 is grown at a growth rate of 0.2 μm / hour by a K-cell to form a p-type base layer. Subsequently, while doping Sb with an ionized Knudsen cell, Ge is grown at 5000 ° by a Ke-cell to form an n-type collector layer 4. Ge was grown near the emitter end of the base by an electron gun growth method, and Ge was grown near the collector end by a K-cell. By this growth method, an ideal Ge / GaAs HBT could be manufactured.

In the present embodiment, the base layer having a thickness of 1000 ° is grown by an electron gun growth method and a K-cell growth method by half, that is, by 500 °. However, the present invention is not limited to this. However, when the transistor operates, a depletion layer is formed in the base layer on both the emitter layer side and the collector layer side, and the boundary between the electron gun growth and the K-cell growth has a film thickness ratio by both growth methods so as not to cover the depletion layer. Alternatively, it is desirable in terms of characteristics to consider impurity concentration.

(Effect of the Invention) According to the present invention, an ideal Ge / GaAs HBT having a small collector leak current can be manufactured.

[Brief description of the drawings]

FIG. 1 is a structural diagram of a Ge / GaAs HBT according to the present invention. FIG. 2 is a structural diagram of a conventional Ge / GaAs HBT. FIG. 3 is a diagram showing a common emitter voltage characteristic of a conventional Ge / GaAs HBT. FIG. 4 is a diagram showing current-voltage characteristics between an emitter and a base and between a base and a collector of an HBT produced by a conventional electron gun growth method using a germanium growth method with a growth rate of 2 μm / hour. FIG. 5 is a current-voltage characteristic diagram between the emitter and the base and between the base and the collector of the HBT manufactured by the growth method using the Knudsen cell growth method at a growth rate of several thousand angstroms / hour. In the figure, 1 ... n-type GaAs layer, 2 ... p-type Ge layer grown by E-gun, 3 ... p-type Ge layer grown by K cell, 4 ... n-type Ge grown by K cell
Layer 5 Collector electrode 6 Base electrode 7 Emitter electrode 8 n-type GaAs layer 9 E-grown p-type Ge layer 10 E-grown n-type Ge layer 11 ... collector electrode, 12 ... base electrode, 13 ... emitter electrode.

Claims (1)

(57) [Claims] 1. A method of manufacturing an npn-type heterojunction bipolar transistor in which germanium as a base and collector layers is formed on gallium arsenide as an emitter layer,
Manufacturing of a heterojunction bipolar transistor characterized in that germanium in contact with the emitter layer of the base layer uses molecular beam epitaxial growth using an electron gun, and germanium in contact with the collector layer uses molecular beam epitaxial growth using a Knudsen cell. Method.